This page provides definitions for each of the characters in our matrix, and justifies codings in particular taxa where relevant. Further citations for codings that are not discussed in the text can be viewed by browsing the morphological dataset on MorphoBank (project 3262).
Alongside its definition, each character has been mapped onto a tree. Any of the optimal trees can be selected by modifying the tree number listed above each diagram. Each tip is labelled according to its coding in the matrix. These states have been used to reconstruct the condition of each internal node, using the parsimony method of Brazeau et al. (2018) as implemented in the R package Inapp.
We emphasize that different trees give different reconstructions. The character mappings are not intended to definitively establish how each character evolved, but to help the reader quickly establish how each character has been coded, and to visualize at a glance how each character fits onto a given tree. Click here to hide the character reconstructions below.
Click on the numbers by a node for details
Steps incurred at node 74:
25Body organization: Serial repetition168Sclerites: Ornament: Concentric ornament172Sclerites: Composition: Mineralogy
The embryonic shell or protegulum is secreted by the embryo immediately before hatching. Corresponds to character 12 in Vinther, Parry, Briggs, & Van Roy (2017).
Dentalium: The shell does not form until the trochophore larval stage, which has been exquisitely described in Antalis (Wanninger & Haszprunar, 2001).
This shell field is initially disc-like, subsequently expanding to fuse ventrally and produce the cylindrical protoconch. The prototroch is clearly delineated fro the telotroch in post-metamorphic juveniles (Wanninger & Haszprunar, 2001).
Gasconsia: The earliest shell is not described by Hanken & Harper (1985) or Watkins (2002).
Namacalathus: Inapplicable insofar as reproduction occurs by budding; there is no evidence for a free-living larval stage. Nevertheless, the presence of a sexual reproductive phase in addition to asexual reproduction cannot be discounted.
Neopilina: Not coiled, as stated in Lemche & Wingstrand (1959), but bulbous (Lindberg, 1985,Wingstrand (1985)).
Novocrania: Shell not secreted until after metamorphosis (Popov et al. 2010). Freeman & Lundelius (1999) report a Craniops-like larval shell in fossil “Crania”, but observe that Quaternary [Novo]crania no longer exhibit a larval shell.
Paramicrocornus: “The initial part of the conch appears to be a simple apex without clearly delineated protoconch” (Z.-L. Zhang, Skovsted, & Zhang, 2018), though it is not clear from illustrated figures whether an embryonic shell contiguous with the adult shell was present.
Pojetaia runnegari: Prodissoconch I probably demarcated by first growth line (B. Runnegar & Bentley, 1983).
Tonicella: On hatching, the polyplacophoran larva lacks a shell field.
Shell fields develop during the trochophore larva stage. The larva of the chiton Mopalia has two distinct shell fields: that anterior to the prototroch will develop into the first shell plate; the one posterior to the prototroch becomes the subsequent plates (Wanninger & Haszprunar, 2002a).
This disc-shaped posterior plate, whose position corresponds to the conchiferan shell field, bears a polygonal ornament and is subdivided by a series of grooves that prefigure the adult shell plates (Wanninger & Haszprunar, 2002a).
The brephic shell is the shell possessed by the young organism (see Ushatinskaya & Korovnikov 2016R and Popov et al. 2010 for discussion of terminology).
Micrina resembles linguliforms (Holmer et al. 2011): in both, the brephic mitral shell has one pair of setal sacs enclosed by lateral lobes, whereas the brephic ventral shell has two lateral setal tubes.
Paterimitra and Salanygolina have “identical” ventral brephic shells (Holmer et al 2011), resembling the shape of a ship’s propeller.
Haplophrentis is coded following typical hyoliths, which have a spherical brephic shell; Pedunculotheca’s, in contrast, is seemingly cap-shaped.
Askepasma toddense: Renoid – see fig. 4B3 in Topper et al. 2013T.
Clupeafumosus socialis: The flat larval shell of Clupeafumosus resembles that of Micrina in outline (Topper et al. 2013R; cf. Holmer et al. 2011).
Coolinia pecten: See fig. 3 in Bassett et al. 2017.
Craniops: The embryonic shell is more or less circular in outline – see Freeman & Lundelius, 1999, fig. 6A.
Cupitheca holocyclata: The impression of the larval shell on the operculum is flat and disc-like (Skovsted et al., 2016). The fusiform ‘protoconch’ (H.-J. Sun, Malinky, Zhu, & Huang, 2018) likely represents a larval (rather than brephic) shell.
Haliotis: Subspherical (Auzoux-Bordenave et al., 2010).
Lingula: See fig. 159 in Williams et al. 1997.
Lingulellotreta malongensis: Disc-like (G.-X. Li & Holmer, 2004).
Mickwitzia muralensis: Trifoliate appearance results from prominent attachment rudiment and bunching of setal sacs (Balthasar 2009T).
Micromitra: Subtriangular – essentially round.
Mytilus: Flat (though split into two via non-mineralized ligament) (Kniprath, 1980).
Neopilina: Appears cap-shaped and relatively flat in Lindberg (1985), but more bulbous in Wingstrand (1985).
Pelagodiscus atlanticus: See e.g. fig 169 in Williams et al. (1997).
Pojetaia runnegari: Flat and disc-like – though bivalved (B. Runnegar & Bentley, 1983).
Tonicella: Disc-like, subdivided by transverse grooves (Wanninger & Haszprunar, 2002a).
[3] Embryonic shell extended in larvae
Character 3: Brephic shell: Embryonic shell extended in larvae
Many taxa add to their embryonic shell (the protegulum possessed by the embryo upon hatching) during the larval phase of their life cycle. The shell that exists at metamorphosis, marked by a halo or nick point, is variously termed the “first formed shell”, “metamorphic shell” or “larval shell” (Bassett & Popov 2017).
Bactrotheca: There is a small ridge and a change in surface ornament at the end of the larval shell (Dzik, 1980).
Clupeafumosus socialis: Described by Topper et al. (2013R).
Craniops: Prominent nick; see Freeman & Lundelius 1999, fig. 6A.
Cupitheca holocyclata: Prominent nick (Skovsted et al., 2016).
Eoobolus: Nick point indicated by arrows in fig. 1 of Balthasar (2009T).
Neopilina: “delimited from the surrounding adult shell by the innermost (first) concentric ridges of the periostracum” (Wingstrand, 1985).
Paramicrocornus: Not clearly delineated (Z.-L. Zhang et al., 2018), so either inapplicable or undifferentiated.
Pedunculotheca diania: The flattened region at the umbo of the ventral valve in smaller specimens conceivably represents an embryonic shell, though it may alternatively represent a cicatrix or colleplax-like structure.
Pitting of the larval shell characterises acrotretids and their relatives. Pustules occur on Paterinidae. See Character 3 in Williams et al. (2000) tables 5–6.
Askepasma toddense: Indented with hexagonal pits (Williams et al. 1998T, appendix 2).
Clupeafumosus socialis: “Larval shells on both valves […] are covered by fine, shallow pits” – Topper et al. 2013R.
Cupitheca holocyclata: Perfectly smooth (Skovsted et al., 2016).
Siphonobolus priscus: “Smooth brephic shell” – Popov et al. 2009.
[5] Larval attachment structure
Character 5: Brephic shell: Larval attachment structure
Embryonic shells of Micrina and certain linguliforms exhibit a transversely folded posterior extension that speaks of the original presence of a pedicle in the embryo.
This is independent of the presence of an adult pedicle, which may arise after metamorphosis.
Clupeafumosus socialis: The larval shell embraces the pedicle foramen, suggesting a larval attachment. See fig. 4 of Topper et al. (2013R).
Cupitheca holocyclata: A pedicle is not inferred by Skovsted et al. (2016), and is difficult to reconcile with the apical morphology documented by H.-J. Sun et al. (2018).
Eoobolus: Lobe related to the attachment rudiment (Balthasar 2009T, fig. 2).
Lingulellotreta malongensis: The pedicle foramen intersects the brephic shell (Holmer et al., 1997; G.-X. Li & Holmer, 2004), suggesting larval attachment.
Mickwitzia muralensis: Note the posterior lobe related to the attachment rudiment in fig. 2 of Balthasar 2009T.
Siphonobolus priscus: Interpreted as having planktotrophic (and thus non-attached) larvae (Popov et al. 2009).
[6] Setulose
Character 6: Brephic shell: Setulose
The protegulum of Micrina is penetrated with canals that were originally associated with setae, a character that it has in common with linguliforms (Holmer et al. 2011).
Botsfordia: “One specimen shows fine capillae running laterally from the posterior tubercles on the dorsal valve (Pl. 3, fig. 5b). This is possibly the imprints of setae.” – Ushatinskaya & Korovnikov 2016R.
Clupeafumosus socialis: Setal bundles interpreted as present in acrotretids by Ushatinskaya (2016P).
Cupitheca holocyclata: Absent (Skovsted et al., 2016).
Lingulellotreta malongensis: Possible suggestion of setal sacs present on brephic shell (Holmer et al., 1997; G.-X. Li & Holmer, 2004), but outline inadequately preserved to code with confidence; treated as ambiguous.
Mickwitzia muralensis: Four setal sacs.
[7] Setal sacs
Character 7: Brephic shell: Setal sacs
Setal sacs are recognizable as raised lumps on the juvenile shell (see Bassett and Popov 2017).
Micrina and linguliforms have setal sacs on their mitral/dorsal embryonic shell, whereas these are absent in Paterimitra (Holmer et al 2011).
Botsfordia: A single pair of low tubercles are (Ushatinskaya & Korovnikov 2016R state “may be”) located in the middle region of the dorsal and the ventral brephic valve; these are interpreted as a single pair of setal sacs, with the identity of the (dorsally unpaired) tubercles uncertain.
Clupeafumosus socialis: Setal bundles interpreted as present in acrotretids by Ushatinskaya (2016P).
Lingula: Lingulids’ larval setae are not arranged in bundles (Carlson 1995).
Lingulellotreta malongensis: Possible suggestion of setal sacs present on brephic shell (Holmer et al., 1997; G.-X. Li & Holmer, 2004), but outline inadequately preserved to code with confidence; treated as ambiguous.
Novocrania, Pelagodiscus atlanticus: Three pairs (Carlson 1995).
[8] Number
Character 8: Brephic shell: Setal sacs: Number
Two pairs on e.g. Coolina; one on e.g. Micrina.
Botsfordia: “larval shell with one to three apical tubercles in ventral valve and two in dorsal valve” (Williams et al. 2000) – if these correspond to setal sacs, then we interpret this as equivalent to one pair.
In B. minuta, the ventral valve bears a single medial tubercle (which in figured material seems to have two bilaterally symmetrical fields), whereas the dorsal valve bears two apical tubercles (G.-X. Li & Holmer, 2004) – supporting the interpretation of a single pair of setal sacs.
Clupeafumosus socialis: Two pairs identified in acrotretids by Ushatinskaya (2016P).
Mickwitzia muralensis: See fig. 2 in Balthasar 2009T.
Novocrania, Pelagodiscus atlanticus: Three pairs (Carlson 1995).
Siphonobolus priscus: Two pairs of setal sacs (Popov et al. 2009).
4.2 Larval setae: Paired bundles [9]
Character 9: Larval setae: Paired bundles
Annelid chaetae are equivalent to the bundled setae expressed in certain brachiopod larvae. See character 12 in Vinther, Van Roy, & Briggs (2008).
Lüter (2000) demonstrates that the setae of larval and adult brachiopods exhibit fundamental structural differences and are conceivably not homologous structures. Larval setae are thus described separately.
Although preservation of setae in fossil brachiopods is exceptional, their presence can be inferred from shelly material (see Holmer, Skovsted, & Brock (2006)).
The girdle elements of aculiferan molluscs include chitinous material that is secreted by microvilli; following Vinther et al. (2017), these are coded as potential homologues of setae.
Acaenoplax hayae: The spines that adorn the ridges (???) are interpreted as equivalent to polyplacophoran girdle elements.
Acanthotretella spinosa: Note that the setae do not obviously emerge from tubes, leading Holmer and Caron to question their homology with the setae of other taxa (Heliomedusa, Mickwitzia).
Both valves of Acanthotretella were covered by long spine-like and shell penetrating setae. The setae of A. decaius are usually preserved along anterior and anterolateral margins (Hu et al. 2010).
Amathia: The teeth of the Bryozoan gizzard have been homologized with annelid setae (Gordon, 1975).
Clupeafumosus socialis: Setal bundles interpreted as present in acrotretids by Ushatinskaya (2016P).
Flustra: A gizzard is not present in all bryozoans, and has not been reported in Flustra.
Kulindroplax perissokomos, Phthipodochiton thraivensis, Glaphurochiton carbonarius: The girdle elements of aculiferan molluscs include chitinous material that is secreted by microvilli; following Vinther et al. (2017), these are coded as potential homologues of setae.
Lingulellotreta malongensis: “Setae appear short, delicate, and are closely fringed with the entire
mantle margin, hardly extending beyond the edge of shell” – Zhang, Shu, Han, & Liu (2005).
Novocrania: “Adult craniids are without setae (a feature shared with the thecideides, the
shells of which are also cemented).” – Williams et al. 2007.
Orthrozanclus: The sclerites of Orthrozanclus are interpreted as being homologous to those of Halkieria.
Orthrozanclus occurs in preservational regimes that preserve sclerites in annelids and Wiwaxia, so additional seta-like sclerites – whose presence cannot be evaluated in Halkieria – are taken to be genuinely absent.
Polysacos vickersianum: The spinose sclerites of multiplacophorans are generally considered to represent modified shell plates rather than girdle elements (???, Conway Morris (2006)).
(???) argues that the spines of Polysacos are homologous with polyplacophoran girdle elements.
However, aesthete canals form by the inclusion of the secretory mantle within the growing valve (Baxter, Jones, & Sturrock, 1987), which points to a fundamentally non-seta-like growth mechanism; rather than secretion by basal microvilli, multiplacophoran spines evidently grow by basal accretion without periodic replacement.
As such, the existence of girdle elements homologous to setae is not demonstrated by available fossil material.
Siphogonuchites multa: The nature of the spicules that constitute the Siphogonuchites shell is uncertain. We treat them here as homologous to chiton girdle elements, following Conway Morris & Chapman (1996), Bengtson (1992) and Vinther et al. (2017).
An equivalence to halkieriid sclerites is not apparent: sclerites must have been added to the edge of the Siphogonuchitid shell during growth, requiring an increase in the number of sclerite ‘rows’; and they do not follow a quincuncial arrangement in a straightforward manner.
The internal ornament of parallel lines (Bengtson, 1992; Conway Morris & Chapman, 1996) recalls the longitudinal chambers within microvillar-secreted setae, but occur on the inner surface of phosphatized chambers, so probably have a different origin.
Siphonobolus priscus: Phosphatised setae emerge from hollow spines (Popov et al. 2009).
Sipunculus: The absence of chitin or microvillar lineations in sipunculan hooks argues against their interpretation as setae, but they are coded as conceivable homologues, with these characteristics treated separately.
Tonicella: The girdle elements of certain polyplacophorans are chitinous and secreted by microvilli (Fischer, Maile, & Renner, 1980; Leise, 1988; Leise & Cloney, 1982); it is therefore likely that they are homologous with the setae of other lophotrochozoans.
They are not homologous with the shell; they exhibit a distinct mode of secretion and have a different organic scaffold (Treves, Traub, Weiner, & Addadi, 2003, Ehrlich (2010)).
The majority of lophotrochozoan sclerites bear a characteristic striated texture that denotes their secretion by basal microvilli (Butterfield, 1990). The seta-like hooks of sipunculans lack this texture, suggesting that they may not be homologous with other setae.
Wiwaxia corrugata: The loose spacing of pyrite infills of microvillar canals in Wiwaxia sclerites (Smith, 2014) argues against a close-packed arrangement.
[14] Organic constituent
Character 14: Adult setae: Composition: Organic constituent
The majority of lophotrochozoan sclerites are chitinous, occasionally hosting secondary biominerals.
Canadia spinosa, Wiwaxia corrugata: Presumed chitin due to preservational character.
Leptochiton: “The spicules and scales […] are composed of aragonite and a highly glycosylated proteinaceous organic matrix” (???; Treves et al., 2003).
Sipunculus: Enzymatic test for chitin proved negative (Rice, 1993).
[15] Enamel
Character 15: Adult setae: Composition: Enamel
Certain setae are encapsulated in a 20 nm wide electron dense layer, termed “enamel” by Gustus & Cloney (1973). Enamel may be absent in larval setae (Lüter, 2003); this character refers to the condition in adult setae.
Setae penetrate the valves of many brachiopods. In certain taxa, they are apparent only at the margins of the valves, in association with the commissure, being reduced or lost over the surface of the shell.
The ‘fascicles’ of Vinther et al. (2017) are a specific case of the ‘bundles’ described here.
Acaenoplax hayae: Strictly, in transverse rows (???), but in view of the serial repetition this state is deemed appropriate.
Calvapilosa kroegeri: No zonation evident (Vinther et al., 2017).
Chaetoderma: Repetition only evident in larvae (???).
Eccentrotheca: Skovsted et al (2011) assumed the setae may have been present along the margin of the adapical opening, but there is no fossil evidence.
Glaphurochiton carbonarius: Girdle at margin of organism (Hoare & Mapes, 1986).
Heliomedusa orienta: Throughout the shell – see Williams et al. 2007 – causing the pustulose appearance remarked upon by Chen et al. 2007.
Character 18: Adult setae: Distribution: Present on anteriormost segment
This character attempts to reflect character 115 in L. A. Parry, Edgecombe, Eibye-Jacobsen, & Vinther (2016), as modified by (???). This character seeks to capture the fact that both Canadia and Phragmochaeta are interpreted as bearing chaetal bundles on their anterior segments (???). Wiwaxia does too.
I treat the character as transformational, coding it as inapplicable where trunk chaetae or parapodia are absent, as it is not possible to independently verify the ancestral state of this character.
[19] Internal constitution
Character 19: Adult setae: Internal constitution
Sipunculan “setae” are basally invaginated, suggesting that they may not be homologous with annelid chaetae. Certain aculiferans also exhibit basally hollow sclerites (???, character 6).
Acaenoplax hayae: No indication of basal invagination (???).
Amathia: Cytoplasmic intrusion into a central cavity (Gordon, 1975).
Calvapilosa kroegeri: Hollow conical sclerites (Vinther et al., 2017).
Kulindroplax perissokomos: The sclerites are described as blade-like (Sutton et al., 2012); their concavo-convex shape presumably relates to the surface of the blade, rather than being intended to imply a deep basal cavity.
Hooked chaetae arise through the reorientation of the chaetoblast during secretion (Hausen, 2005). (???) and L. A. Parry et al. (2016) distinguish falcate (sickle-shaped) hooks (characters 121 and 98 respectively), dentate hooks (characters 122 and 92) and uncini (characters 123 and 94) as fundamentally different types of chaetae. A dentate hook, however, can be seen as a falcate hook with additional adrostral teeth or processes (???). We therefore code simply for the presence of apical curvature in any chaetae, with a view that a gain of a ‘hook’ represents an evolutionary novelty that might then be expressed in various locations and complemented by the addition of subsidiary dentition (i.e. adrostral hooks).
For terminology, see (???) and (???).
Capitella: Present in Notomastus (Capitellidae) (Hausen, 2005, fig. 4).
Serpula: Following coding of character 80 in (???); uncini scored as present by L. A. Parry et al. (2016).
[22] Capitium
Character 22: Adult setae: Capitium
Character 81 in (???). The capitium is a region on the convex surface of the rostrum (if present) that contains containing multiple teeth, each secreted by an individual microvillus (???, ???; Hausen, 2005), and in a consistent orientation with the margin of the chaeta.
Capitella: Present in Notomastus (Capitellidae) (Hausen, 2005, fig. 4).
[23] Projecting knobs
Character 23: Adult setae: Projecting knobs
Terebratulids and discinids instead exhibit knob-like individual spines. These are distinct from the rings of spines that fringe lingulid setae.
Pelagodiscus atlanticus: Discinisca sports individual peripheral spines (Lüter, 2003; Williams et al., 1997).
Note that the “embryonic” setae of Discinids correspond to the “larval setae” of other brachiopods, and the “larval setae” of juvenile discinids correspond to adult setae (Lüter, 2003).
Lingulid setae bear crown-like rings of fine spines delimiting vertical sections, recalling the nodes of Equisetum stems. These arise by the addition of an additional circlet of microvilli (see Lüter, 2000, fig. 1e).
Character 25: Body organization: Serial repetition
Serial repetition in adult, whether expressed in valves, soft tissues or exoskeletal elements. See character 13 in Rouse (1999); 19 in Vinther et al. (2008); 38 in Haszprunar (1996); 40–41 in Sutton & Sigwart (2012); Wanninger (2009).
Acaenoplax hayae: Serial repetition of lobes and spine rows (???).
Bactrotheca: The soft anatomy of this taxon is unknown, so it is impossible to rule out the presence of serial repetition.
Calvapilosa kroegeri: Conceivably evident in soft tissue that is not preserved, e.g. gills.
Chaetoderma: Present in larval stages only (???).
Dailyatia: Unknown whether sclerites are serially repeated, or whether metameres were present in underlying soft anatomy.
Halkieria evangelista: Elements of the Halkieria scleritome adhere to a quincunx arrangement, with different spacing of elements in each zone; there is no evidence of a metameric arrangement.
Namacalathus, Wirenia: Not evident.
Neopilina: Serially repeated gills.
Odontogriphus omalus: Repetition of ctenidia (???).
Orthrozanclus: Coded following Halkieria.
Pelagiella: Not apparent in distribution of setae (Thomas & Vinther, 2012).
Yilingia spiciformis: Present (Chen et al., 2019).
[26] Annulae
Character 26: Body organization: Annulae
The trunk of Sipunculus and many annelid worms bear annulations.
[27] Subdivided head
Character 27: Body organization: Subdivided head
The annelid head comprises a differentiated prostomium and peristomium. See character 119 in Parry & Caron (2019).
Canadia spinosa, Serpula: Following Parry & Caron (2019).
Capitella: Fused prostomium and peristomium, following Parry & Caron (2019).
Phthipodochiton thraivensis: Seemingly present, though foot unequivocally absent (Sutton & Sigwart, 2012; Sutton et al., 2012).
Wirenia: Present and flanked by a distinct set of spicules in Epimenia(Okusu, 2002).
[29] Foot
Character 29: Body organization: Pedal groove: Foot
See characters 8 in Haszprunar (1996); 4 in Vinther et al. (2008); 137 in Rouse (1999); 21 in Buckland-Nicks (2008); 37 in Sutton & Sigwart (2012); 1, 3 and 4 in Haszprunar & Wanninger (2008).
It is assumed that the adult foot is homologous with (and thus contingent on) the larval foot.
Acaenoplax hayae: Secondarily lost; represented by medial groove.
Sipunculus: LISTED AS PRESENT IN Smith (2012a): WHY?
Yilingia spiciformis: The associated ichnofossils contain transverse structures that are not consistent with production by a ventral foot (Chen et al., 2019).
[30] Coelom
Character 30: Body organization: Coelom
Bactrotheca: The soft anatomy of this taxon is unknown, so it is impossible to determine the presence of a coelom.
Character 31: Body organization: Coelomoducts: Number
Character 27 in Haszprunar (2000). Coelomoducts are excretory organs derived from the coelom, also in some cases serving as genital ducts (gonoducts); they replace (and may resemble) nephridia (Goodrich, 1945).
Flustra: Multiple ciliated ducts leading to a common gonopore (Goodrich, 1945).
Loxosomella: Two coelomoducts pass outwards, meet, and open by a common pore (Goodrich, 1945).
Phoronis: “large coelomic funnels serving as genital ducts” (Goodrich, 1945).
[32] Gills
Character 32: Body organization: Gills
Gills (or ctenidia) surround the molluscan foot.
Character 1.59–60, 2.09, 4.49 in von Salvini-Plawen & Steiner (1996); 10–11 in Haszprunar (2000); 45 in Sutton & Sigwart (2012).
Acaenoplax hayae: The posterior projections are interpreted as resembling the gill folds of solenogasatres (???).
Calvapilosa kroegeri: Not preserved, though presumably present.
Character 34: Body organization: Circulatory system
After character 23 in Haszprunar (1996); 24 in Haszprunar (2000); 41 in Rouse (1999); 16 in A. H. Scheltema (1993); 16 in Vinther et al. (2008); 5 in Haszprunar & Wanninger (2008).
Flustra, Amathia: As Brachiopods, sipunculans and relatives (Ruppert & Carle, 1983).
Loxosomella, Tonicella, Dentalium: See Haszprunar & Wanninger (2008).
Sipunculus: Open circulatory system.
4.5 Pedicle
[35] Presence
Character 35: Pedicle: Presence
The brachiopod pedicle is a fleshy protuberance that emerges from the posterior part of the body wall – as denoted in fossil taxa by its occurrence between the dorsal and ventral valves.
It is important to distinguish the pedicle from the “pedicle sheath”, a tubular extension of the umbo that grows by accretion from an isolated portion of the ventral mantle. For discussion see Holmer et al. 2018T and Bassett and Popov 2017.
Acanthotretella spinosa: The attachment structure of Acanthotretella originates at the margin of the dorsal and ventral valves; although it emerges from the umbo of the ventral valve, the presence of an internal pedicle tube betrays its identity as a pedicle, rather than a pedicle sheath.
The pedicle of Acanthotretella emerges from a short extension of the umbo of the ventral valve. This extension is contiguous with the valve and presumably grew by accretion; its position and continuity with the valve suggest its interpretation as a pedicle sheath that is superseded as an attachment structure. On the other hand, its continuity with the internal pedicle tube suggests that is may represent an independent organ.
Bactrotheca: The apex of Bactrothecadeleta is pointed (Novak, 1891).
Botsfordia: Pedicle foramen was not necessarily occupied by a pedicle (though it presumably was).
Clupeafumosus socialis: A pedicle was presumably present, but only the foramen is preserved.
Cotyledion tylodes: The stalk is conceivably homologous with the brachiopod pedicle, but this possibility is impossible to test.
Craniops: Attached apically by cementation.
Cupitheca holocyclata: Not possible to reconcile with decollation.
Flustra: Grows directly onto the substrate.
Heliomedusa orienta: “It seems unlikely that H. orienta possessed a pedicle that attached it to
the soft seafloor, like most other Chengjiang brachiopods.” …
“The putative pedicle illustrated by Chen et al. (2007: Figs 4, 6, 7) in fact is the mold of a three-dimensionally preserved visceral cavity” – Zhang et al. 2009.
Lingulosacculus: The absence of a pedicle is inferred from the absence of an internal pedicle tube, and the absence of a pedicle at the hinge.
Loxosomella: The stalk corresponds to the molluscan foot, rather than a pedicle.
Mickwitzia muralensis: An attachment structure is inferred based on the presence of an opening (Balthasar 2004); this is assumed to have been homologous with the brachiopod pedicle.
Micrina: The prominent foramen between artificially articulated valves is taken to imply the presence of a pedicle (Holmer, Skovsted, Brock, Valentine, & Paterson, 2008).
Micromitra: The presence of a pedicle is indicated by the propensity of Micromitra to attach to hard substrates, such as sponge spicules (Holmer & Caron, 2006).
Namacalathus: There is no obvious way to homologise the attachment structure with the ventral pedicle of brachiopods.
Nisusia sulcata: Has a pedicle, rather than a pedicle sheath as in Kutorgina (Holmer et al. 2018E; Holmer et al. 2018T).
Paterimitra: “Paterimitra is interpreted to have attached to hard substrates via a pedicle that emerged through the small posterior opening” – Skovsted et al. 2009.
Phoronis: The tube-bearing stalk of phoronids arises as an eversion of the metastomal sac, a markedly different origin from the brachiopod pedicle, which arises from a terminal attachment disc (Young, 2002); the structures are of dubious homology.
Siphonobolus priscus: Presumed present, based on ventral foramen with colleplax.
Sipunculus: Absent; there is no clear basis to homologise the larval attachment structure of certain sipunculans with a pedicle.
[36] Constitution
Character 36: Pedicle: Constitution
The pedicle of certain chengjiang rhynchonelliforms comprises “densely stacked, three dimensionally preserved, tabular discs” (Holmer et al. 2018E).
This contrasts with the uniform (‘massive’) pedicles of living taxa.
Antigonambonites planus: Biomineralized (Holmer et al. 2018E).
Terebratulina: Extant rhynconellid pedicles are massive, consisting of a thick outer chitinous cuticle, a pedicle epithelium, and a core composed of collagen fibres and cartilage-like connective tissue (Holmer et al. 2018E).
[37] Biomineralization
Character 37: Pedicle: Biomineralization
Kutorgina chengjiangensis: The tabular discs that make up the pedicle “clearly have a pronounced three-dimensional preservation and may have been partly mineralized.” –Holmer, Zhang, Topper, Popov, & Claybourn (2018b).
Micromitra: A pedicle has not been observed in biomineralized material (Williams, Popov, Holmer, & Cusack, 1998b), indicating an originally non-mineralized constitution.
[38] Bulb
Character 38: Pedicle: Bulb
A bulb is an expanded region of the distal pedicle, often embedded into the sediment to improve anchorage.
Acanthotretella spinosa: Holmer and Caron (2006) interpret the presence of a bulb as tentative; we score it as ambiguous.
[39] Distal rootlets
Character 39: Pedicle: Distal rootlets
Observed in Pedunculotheca and Bethia (Sutton et al 2005).
[40] Tapering
Character 40: Pedicle: Tapering
Holmer et al. (2018T) remark that the tapering aspect of the Nisusia pedicle recalls that of certain Chengjiang taxa (Alisina, Longtancunella) whilst distinguishing it from many other taxa (Eichwaldia, Bethia) in which the pedicle is a constant thickness.
Antigonambonites planus: Tapered pedicle sheath with holdfast.
Pedunculotheca diania: The pedicle thickness gradually typering from the apex of the shell to the holdfast.
[41] Coelomic region
Character 41: Pedicle: Coelomic region
Certain brachiopods, such as Acanthotretella, exhibit a coelomic cavity within the pedicle or pedicle sheath.
Treated as transformational as it is not clear that either state is necessarily ancestral.
Nisusia sulcata: A coleomic canal is inferred based on the ease with which the pedicle is deformed (Holmer et al. 2018E), but its presence is not known for certain so is coded ambiguous.
[42] Surface ornament
Character 42: Pedicle: Surface ornament
Annulations are regular rings that surround the pedicle, and are distinguished from wrinkles, which are irregular in magnitude and spacing, and may branch or fail to entirely encircle the pedicle.
Acanthotretella spinosa: “The pedicle surface is ornamented with pronounced annulated rings, disposed at intervals of about 0.2 mm”.
Alisina: “It appears that the pedicle lacks a coelomic space and is distinctly annulated, with densely stacked tabular bodies” – Zhang et al. 2011A.
Antigonambonites planus: “The emerging pedicle has a consistent shape in all the available specimens and is strongly annulated and distally tapering” – Holmer et al. 2018E.
Kutorgina chengjiangensis: “Pronounced concentric annular discs disposed at intervals of 0.6–1.0 mm” – Zhang et al. (2007b).
Lingulellotreta malongensis: Regularly annotated (see fig. 14.9 in Hou et al. 2017).
Longtancunella chengjiangensis: “The preserved pedicle has condensed annulations” – Zhang et al. 2011T.
Nisusia sulcata: The “strong annulations” vary significantly in transverse thickness (Holmer et al. 2018E), so it is not clear whether these represent true annulations or wrinkles.
Yuganotheca elegans: Annulations present in median collar.
[43] Nerve impression
Character 43: Pedicle: Nerve impression
In certain taxa the impression of the pedicle nerve is evident in the shell. See character 28 in Williams et al. (1998T) appendix 1. Care must be taken not to code an impression as absent when the preservational quality is insufficient to safely infer a genuine absence. Treated as neomorphic as the presence of an innervation is considered a derived state.
Alisina: Not described by Williams et al. 2000.
Askepasma toddense, Micromitra, Glyptoria, Kutorgina chengjiangensis, Salanygolina: Following Williams et al. 1998T, appendix 2.
Botsfordia: Documented by Skovsted et al. 2017.
Clupeafumosus socialis: Coded as absent in Acrotretidae (Williams et al. 2000, table 6).
Lingula: Present in many lingulids (Williams et al. 2000), and coded as present in Lingulidae (Williams et al. 2000, table 6).
Lingulellotreta malongensis: Coded as present in Lingulellotretidae (Williams et al. 2000, table 6).
Mummpikia nuda: Balthasar (2008, p. 274) identifies a canal as a probable impression of a pedicle nerve.
Nisusia sulcata, Orthis: Not reported in Williams et al. 2000.
Pelagodiscus atlanticus: Coded as present in Discinidae (Williams et al. 2000, table 6).
Siphonobolus priscus: Coded as absent in Siphonotretidae (Williams et al. 2000, table 6).
Phthipodochiton thraivensis: Indirectly implied (Sutton et al., 2012).
[47] Sac opening
Character 47: Mantle cavity: Sac opening
Caudofoveate and solenogaster aplacophorans can be distinguished based on the direction that their mantle cavity opens (Sutton et al., 2012).
Wirenia, Chaetoderma, Kulindroplax perissokomos: Sutton et al. (2012).
Phthipodochiton thraivensis: Indirectly interpreted as posterioventral (Sutton et al., 2012).
[48] Pallial line
Character 48: Mantle cavity: Pallial line
The pallial line is a mark on inner surface of a shell reflecting the attachment of the mantle.
Conocardium elongatum: Prominent in some rostroconchs (Runnegar, 1978).
Neopilina: Present, marking limit of nacreous layer (McLean, 1979).
4.7 Mantle canals
[49] Presence
Character 49: Mantle canals: Presence
Whether impressed on a shell or expressed solely in soft tissue.
Cupitheca holocyclata: Not observed despite excellent preservation.
Paramicrocornus: Not impressed on valves, despite fine preservation of muscular attachment (Z.-L. Zhang et al., 2018).
Paterimitra: Not evident.
Ussunia: Not preserved along muscle scars (Nikitin & Popov, 1984), presumably owing to quality of preservation rather than genuine absence.
[50] Morphology
Character 50: Mantle canals: Morphology
The morphology of dorsal and ventral canals is identical in all included taxa, so is assumed not to be independent – hence the use of a single character (contra Williams et al. 2000).
For a description of terms see Williams et al. (1997, 2000).
Pinnate = “rapidly branch into a number of subequal, radially disposed canals”
Bifurcate = “vasculalateralia in both valves divide immediately after leaving the body cavity”
Baculate = “extend forward without any major dichotomy or bifurcation” (Williams et al. 1997 p. 418)
Saccate = “pouchlike sinuses lying wholly posterior to the arcuate vasculamedia” (ibid., p412).
Acanthotretella spinosa: Following Table 6, for Siphonotretidae, in Williams et al. (2000).
Alisina, Nisusia sulcata: Following Table 15 in Williams et al. (2000).
Antigonambonites planus: Not reported in Treatise (Williams et al. 2000).
Askepasma toddense: Described as pinnate (at least in ventral valve) by Williams et al. (1998T, p. 250).
Botsfordia, Eoobolus: Following Williams et al. 1998T, appendix 2, and Williams et al (2000), table 8.
Clupeafumosus socialis: Following Table 8 (for Acrotreta) in Williams et al. (2000), and the general pinnate condition for acrotretoids stated in Williams et al. (1997), p. 420.
Coolinia pecten: Not reported in Williams et al. 2000.
Craniops: Not reported from fossil material.
Gasconsia: Williams et al. (2000, table 15) appear to use Palaeotrimerella (as drawn in Williams et al. 1997) as a model for Gasconsia, which pre-supposes a close relationship. We are not aware of any report of mantle canals from Gasconsia itself.
Glyptoria: Following appendix 2 (char. 21) in Williams et al. (1998T).
Heliomedusa orienta: Described as pinnate by Jin & Wang (1992).
Novocrania, Kutorgina chengjiangensis: Following table 15 in Williams et al. (2000) (for Neocrania).
Lingula, Lingulellotreta malongensis: Following table 6 in Williams et al. (2000).
Orthis: Sacculate (sometimes digitate in dorsal valve) (Williams et al. 2000, p716).
Pelagodiscus atlanticus: Following table 6, for Discinidae, in Williams et al. (2000).
Salanygolina: Coded uncertain in appendix 2 in Williams et al. (1998T).
Siphonobolus priscus: Interpreted as baculate, following Havlicek 1982.
Terebratulina: “In modern terebratulides, the vasculamedia are subordinate to the lemniscate or pinnate vasculagenitalia” – Williams et al. 1997.
Tomteluva perturbata: Preservation not adequate to evaluate (Streng 2016).
[51] vascula lateralia
Character 51: Mantle canals: vasculalateralia
We treat the vasculalateralia as equivalent to the vasculagenitalia of articulated brachiopods, allowing phylogenetic analysis to test their proposed homology.
Williams et al (1997) write: “The mantle canal system of most of the organophosphate-shelled species consists of a single pair of main trunks in the ventral mantle (vasculalateralia) and two pairs in the dorsal mantle, one pair (vasculalateralia) occupying a similar position to the single pair in the ventral mantle and a second pair projecting from the body cavity near the midline of the valve. This latter pair may be termed the vasculamedia, but whether they are strictly homologous with the vasculamedia of articulated brachiopods is a matter of opinion. It is also impossible to assert that the vasculalateralia are the homologues of the vasculamyaria or genitalia of articulated species, although they are likely to be so as they arise in a comparable position.”
“In inarticulated brachiopods, two main mantle canals (vasculalateralia) emerge from the main body cavity through muscular valves and bifurcate distally to produce an increasingly dense array of blindly ending branches near the periphery of the mantle (fig. 71.1–71.2).”
Acanthotretella spinosa: Following table 8 (which records presence in Siphonotreta) in Williams et al. (2000).
Alisina, Kutorgina chengjiangensis, Nisusia sulcata: Following table 15 in Williams et al. (2000).
Askepasma toddense, Micromitra: “Laurie (1987) has shown that arcuate vasculamedia were present in the mantles of both valves as were pouchlike vasculagenitalia, especially in the ventral valve” – Williams et al. 1997.
Botsfordia: Following Popov (1992).
Clupeafumosus socialis: Presence indicated in Table 8 (for Acrotreta) in Williams et al. (2000).
Gasconsia: Williams et al. (2000, table 15) appear to use Palaeotrimerella (as drawn in Williams et al. 1997) as a model for Gasconsia, which pre-supposes a close relationship. We are not aware of any report of mantle canals from Gasconsia itself.
Heliomedusa orienta: Present: Williams et al. (2000); Jin & Wang (1992).
Lingulellotreta malongensis: Present (Williams et al. 2000).
Longtancunella chengjiangensis: Presence is possible but requires interpretation that is not unambiguous:
“In the dorsal valve, there can be seen two baculate grooves that arise from the
anterior body wall at an antero-lateral position. These two grooves (Figs 4H, 5D) could be taken to represent the vasculalateralia” – Zhang et al 2007A.
Novocrania: Following table 15 in Williams et al. (2000) (for Neocrania), who write that “Holocene craniides have only a single pair of main trunks in both valves, corresponding to the vasculalateralia”. Williams et al. (2007) reiterate this position (p. 2875), at least for the ventral valve.
Terebratulina, Orthis: = vasculagenitalia.
Pelagodiscus atlanticus: Following Lochkothele (Discinidae), Fig. 43.4a in Williams et al. (2000).
Siphonobolus priscus: Noted in Siphonobolus by Williams et al. (2000), with reference to Havlicek (1982).
Tomteluva perturbata: Preservation not adequate to evaluate (Streng 2016).
Yuganotheca elegans: Based on the figures and sketches in Zhang et al. 2014 (and supplementary material), the mantle canals are interpreted as lateral, with no clear vasculamedia present.
[52] vascula media
Character 52: Mantle canals: vasculamedia
Williams et al. (1997) note that in addition to the vasculalateralia, “Discinisca has two additional mantle canals emanating from the body cavity into the dorsal mantle (vasculamedia).”
These structures are only evident in the dorsal valve for the included taxa, so only a single character is necessary.
Acanthotretella spinosa: Following table 6 (for Siphonotretidae) in Williams et al. (2000).
Alisina, Kutorgina chengjiangensis, Nisusia sulcata: Following table 15 in Williams et al. (2000).
Askepasma toddense: Following table 6 (for Paterinidae) in Williams et al. (2000).
Botsfordia: Following Popov (1992, fig. 2).
Clupeafumosus socialis: Following Hadrotreta schematic in Williams et al. (2000).
Eoobolus: Fig. 5 in Balthasar 2009T.
Gasconsia: Williams et al. (2000, table 15) appear to use Palaeotrimerella (as drawn in Williams et al. 1997) as a model for Gasconsia, which pre-supposes a close relationship. We are not aware of any report of mantle canals from Gasconsia itself.
Glyptoria: Present and divergent (Williams et al. 2000).
Heliomedusa orienta: Present: Williams et al. (2000) p162, Jin & Wang (1992).
Lingula, Lingulellotreta malongensis: Following table 6 in Williams et al. (2000).
Longtancunella chengjiangensis: Reported by Zhang et al. (2007A) though the interpretation is tentative.
Micromitra: Reported by Williams et al. (1998T).
Novocrania: Williams et al. (2000) write “Holocene craniides have only a single pair of main trunks in both valves, corresponding to the vasculalateralia” – an observation reflected in their table 15 (for Neocrania).
But in contrast, Williams et al. 2007, p. 2875, identify the dorsal valve’s canals as a vasculamedia in living cranidds (though both are lateralia in Ordoviian craniides). This character is therefore coded as ambiguous.
Orthis: From idealised morphology in Williams et al. (2000).
Pelagodiscus atlanticus: Following table 6 (for Discinidae) in Williams et al. (2000).
Siphonobolus priscus: Noted in Siphonobolus by Havlicek (1982).
Terebratulina: “In modern terebratulides, the vasculamedia are subordinate to the lemniscate or pinnate vasculagenitalia” – Williams et al. 1997 p417.
Tomteluva perturbata: Preservation not adequate to evaluate (Streng 2016).
Yuganotheca elegans: Based on the figures and sketches in Zhang et al. 2014 (and supplementary material), the mantle canals are interpreted as lateral, with no clear vasculamedia present.
[53] vascula terminalia
Character 53: Mantle canals: vasculaterminalia
Presumed to be connected with setal follicles in life (Williams et al. 1998T). See Williams et al. (2000) for discussion.
Acanthotretella spinosa: Preservation not clear enough to score with certainty (Holmer & Caron 2006).
Alisina: Interomedial vasculaterminalia not reported by Williams et al. (2000).
Askepasma toddense, Micromitra: Peripheral only (Williams et al. 1998T; Williams et al. 2000).
Botsfordia, Eoobolus: Following Williams et al. 1998T, appendix 2.
Glyptoria: Following appendix 2 in Williams et al. (1998T).
Heliomedusa orienta: Inferred from Jin & Wang (1992).
Kutorgina chengjiangensis, Salanygolina: Coded uncertain in appendix 2 in Williams et al. (1998T).
Lingula: Peripheral and medial for all Lingulata (Williams et al. 2000).
Lingulellotreta malongensis: Not described in Williams et al. (2000).
Lingulosacculus: Strong indication of medially directed vasculaterminalia from vasculalateralia; see fig. 1.A1 in Balthasar & Butterfield 2009E.
Novocrania: Peripheral only (Williams et al. 2000, p.158).
Orthis: See schematics in Williams et al. (2000).
Pelagodiscus atlanticus: Following Lochkothele (Discinidae), fig. 43.4a in Williams et al. (2000).
Siphonobolus priscus: Not reported in Havlicek 1982 or Williams et al. 2000.
Terebratulina: Following idealised plectolophous terebratulid of Emig (1992).
4.8 Perioral tentacular apparatus
[54] Presence
Character 54: Perioral tentacular apparatus: Presence
The lophophore is a ring of tentacles that surrounds the mouth. Temereva (2017) suggests that true lophophores must also encompass the anus, which excludes the tentacular apparatus of entoprocts from the definition; as homology between the tentacular apparatuses of entoprocts and other lophophorates has often been assumed, we prefer to take a more inclusive stance and code the structures as potentially homologous.
It is unlikely that the tentacles of annelids and sipunculans correspond to the lophophore, yet homology is not inconceivable. In order that the tentacular apparatus of Haplophrentis can be compared with both organs without prejudice, we capture the presence of a tentacular apparatus in this very broad character, with arguments against homology reflected in separate transformation series.
Cotyledion tylodes: The tentacular crown (Zhang et al., 2013) is interpreted as a lophophore.
Dentalium: The scaphopod captacula is conceivably equivalent to the tentacular apparatus of other lophotrochozoans. It is developmentally pre-oral, and has tentatively been homologised with the pre-oral tentacles of Monoplacophora and Gastropoda (Steiner, 1992), though their musculature and late development suggests instead that they may derive from the molluscan foot, as do the arms of cephalopods (Wanninger & Haszprunar, 2002b).
Character 55: Perioral tentacular apparatus: Origin
The tentacles of annelids and sipunculans originate from a dorsal pair of buds on the prostomium (Adrianov, Malakhov, & Maiorova, 2006), whereas the brachiopod lophophore arises from the second pair of coelomic sacs (Nielsen, 1991).
Dentalium: The captacula arise close to the mouth after metamorphosis (Wanninger & Haszprunar, 2002b), in a position not dissimilar from that of the phoronid tentacles (Santagata, 2004).
Flustra: The tentacles appear at metamorphosis, seemingly from below the corona (=prototroch) (Young, 2002).
Loxosomella: Arising after metamorphosis (Nielsen, 1971).
Novocrania: “At metamorphosis [….] the second pair of coelomic sacs develop small attachment areas at the edge of the dorsal valve and become the lophophore coelom” (Nielsen, 1991)
“The larval lobes are retained during the first steps of metamorphosis and are
subsequently remodeled to form the lophophore and other adult organs” – Altenburger, Wanninger, & Holmer (2013).
Phoronis: At the posterior of the head, at the late larval stage (Santagata, 2004).
Terebratulina: Lophophore of Terebratalia arises post metamorphosis (Young, 2002); lophophore conceivably arising from vesicular bodies at base of apical lobe?
[56] Tentacle disposition
Character 56: Perioral tentacular apparatus: Tentacle disposition
Tentacles may occur along one or both sides of the axis of the lophophore arm (Carlson 1995).
Acanthotretella spinosa: Preservation insufficient to evaluate (Holmer & Caron 2006).
Sipunculus: Both sides in tentacle-breathers such as Themiste(Adrianov et al., 2006; Ruppert & Rice, 1995); only one side in Sipunculus(Adrianov et al., 2006; Ruppert & Rice, 1995).
[57] Tentacle rows per side in trocholophe stage
Character 57: Perioral tentacular apparatus: Tentacle rows per side in trocholophe stage
After Carlson (1995), character 37. Lophophore tentacles are commonly arranged into an ablabial and adlabial row, with ablabial tentacles sometimes added later in development.
Lingula, Pelagodiscus atlanticus, Terebratulina, Phoronis: Following coding for higher taxon in Carlson (1995), appendix 1, character 37.
Novocrania: Following coding for higher taxon in Carlson (1995), appendix 1, character 37. Also states in Williams et al. 2000, p. 158.
[58] Tentacle rows per side in post-trocholophe stage
Character 58: Perioral tentacular apparatus: Tentacle rows per side in post-trocholophe stage
After Carlson (1995), character 37. Lophophore tentacles are commonly arranged into an ablabial and adlabial row, with ablabial tentacles sometimes added later in development (and thus interpreted as a neomorphic addition).
Acanthotretella spinosa: Preservation insufficient to evaluate (Holmer & Caron 2006).
Cotyledion tylodes: Additional row not evident (Zhang et al., 2013).
Heliomedusa orienta: “The lophophoral arms bear laterofrontal tentacles with a double row of cilia along their lateral edge, as in extant lingulid brachiopods” – Zhang et al. 2009.
Kutorgina chengjiangensis: Tentacles “cannot be confidently demonstrated in the available specimens.” – Zhang et al. 2007R.
Novocrania, Lingula, Pelagodiscus atlanticus, Terebratulina, Phoronis: Following coding for higher taxon in Carlson (1995), appendix 1, character 37.
Lingulellotreta malongensis: Single palisade (Zhang et al. 2004N).
Lingulosacculus: Preservation insufficient to evaluate.
Dentalium: The captacula each bear an individual nerve fibre emanating from the cerebral ganglia, which is also associated with the circumoesophageal nerve ring (Sumner-Rooney et al., 2015), recalling the situation in annelids and sipunculans.
Loxosomella: Tentacle nerves originate laterally from the cerebral ganglion, branching three times and leading to a single nerve within each tentacle (Fuchs, Bright, Funch, & Wanninger, 2006).
Character 64: Perioral tentacular apparatus: Musculature
Dentalium: Six to eight elongate muscle cells in core (Shimek, 1988), surrounded by circular muscles (Byrum & Ruppert, 1994).
Novocrania, Lingula, Pelagodiscus atlanticus, Terebratulina: “Inner coelomic epithelium underlain by muscle fibers, or in the tentacles, myoepithelial cells.” – Williams et al. (1997).
Loxosomella: Outer main tentacle muscle; two pairs of inner longitudinal muscles (Fuchs et al., 2006).
Sipunculus: Peripheral to main tentacle cavity (Pilger, 1982).
[65] Forms closed loop
Character 65: Perioral tentacular apparatus: Forms closed loop
Whereas the lophophore of crown-group brachiopods typically forms a closed loop, those of Haplophrentis and Heliomedusa diverge laterally (Moysiuk et al 2017).
Amathia: Ends of arms meet to form closed loop (Temereva & Kosevich, 2016).
Cotyledion tylodes: Tentacles form almost complete circular crown.
Lingulosacculus: Two diverging arms of the lophophore are preserved (Balthasar & Butterfield 2009E).
Longtancunella chengjiangensis: Two distinct, diverging arms reconstructed by Zhang et al. 2007A.
Novocrania, Lingula, Pelagodiscus atlanticus, Terebratulina, Phoronis: Following coding for higher taxon in Carlson (1995), appendix 1, character 55.
4.9 Mouthparts: Buccal organ
[68] Buccal organ
Character 68: Mouthparts: Buccal organ
The buccal organ describes the structures that arise from the larval mouth region. This may include the foregut, which if eversible is termed a proboscis, and whose muscular regions are termed the pharynx (???).
Sipunculans express a buccal organ as larvae, which is lost after metamorphosis (???).
Novocrania, Lingula, Canadia spinosa, Serpula, Capitella: Following closest relative in Parry & Caron (2019).
Sipunculus: Present in larvae, following (???), fig. 83.
Sipunculus, Canadia spinosa, Capitella: Following Parry & Caron (2019).
4.10 Radula [71]
Character 71: Radula
Character 25 in Vinther et al. (2017). Any apparatus comprising multiple denticulate rows arranged serially in the sagittal plane is treated as potentially homologous with the molluscan radula.
Kulindroplax perissokomos: No radula is preserved (Sutton et al., 2012).
Orthrozanclus: The radula has a high preservation potential in Wiwaxia, and is not evident only when it occurs at a different plane to the one that the fossil splits upon. As such, it is difficult to attribute the absence of a radula in Orthrozanclus to non-preservation.
Wiwaxia corrugata: 1.
[72] Extent
Character 72: Radula: Extent
Character 26 in Vinther et al. (2017). The radulae of Wiwaxia and Odontogriphus are conspicuously similar in their configuration.
Wirenia: Many rows in e.g. Plawenia (Amélie H. Scheltema, 2014).
A robust structure (alary process/hyaline shield) attached to the radula, with thickened margins, increasingly labile towards the rear, and constructed from the same material (chitin) as the radular teeth (Smith, 2012b).
Also referred to as a ‘hyaline shield’.
Wiwaxia corrugata: Inferred to be present (Smith, 2012b), but not observed, so coded as ambiguous.
[75] Bolster vesicles
Character 75: Radula: Bolster vesicles
Hollow fluid-filled radula-supporting structures found in Polyplacophora and Monoplacophora (Katsuno & Sasaki, 2008).
[76] Subradular organ
Character 76: Radula: Subradular organ
Character 3g in Waller (1998); Character 58 in Haszprunar (2000).
[77] Heterodonty
Character 77: Radula: Teeth: Heterodonty
Character 29 in Vinther et al. (2017). Inapplicable if multiple lateral teeth are not present.
Calvapilosa kroegeri: Lateral and uncinical teeth, as in chitons (Vinther et al., 2017).
Haliotis: All teeth bear multiple cusps.
[78] Bending plane
Character 78: Radula: Teeth: Bending plane
Character 60 in Ponder & Lindberg (1997); 2.20 in (???).
[79] More teeth per row in larger individuals
Character 79: Radula: Teeth: More teeth per row in larger individuals
Calvapilosa kroegeri: “exact number [of teeth in a row] is difficult to discern” (Vinther et al., 2017).
[80] Lateral tooth base
Character 80: Radula: Teeth: Lateral tooth base
Presence of a distinct base in lateral teeth; see character 9 in Reynolds & Okusu (1999) and 15 in Steiner (1998).
[81] Lateral tooth head
Character 81: Radula: Teeth: Lateral tooth head
In polyplacophorans, the head of the lateral tooth is elaborate or clearly differentiated from the shaft ((???), character 8).
Oh dear! You included the inapplicable token in a neomorphic character!
That’s unlikely to be a good idea: see Brazeau, Smith & Guillerme (2018, Systematic Biology).
Unless you are very sure that you understand the consequences, you should mark the character as Transformational by setting State 0 to [Transformational character], or re-code:
Wirenia
Chaetoderma
[82] Apatite
Character 82: Radula: Teeth: Apatite
Polyplacophoran teeth are reinforced with apatite (Haszprunar, 2000, character 69).
[83] Magnetite
Character 83: Radula: Teeth: Magnetite
The tips of polyplacophoran teeth contain magnetite (Waller, 1998, character 4e).
4.11 Digestive tract
[84] Prominent pharynx
Character 84: Digestive tract: Prominent pharynx
Hyoliths exhibit a prominent protrusible muscular pharynx at the base of the lophophore (Moysiuk et al. 2017). This is considered as potentially equivalent to the anterior projection of the visceral cavity in Heliomedusa, and, by extension, in Lingulosacculus and Lingulotreta.
Calvapilosa kroegeri: Not evident (Vinther et al., 2017), and interpreted as absent based on position of radula.
Canadia spinosa: The interpretation of a possible pharynx is ambiguous (???, ???).
Capitella: ‘Prominence’ is perhaps arguable in Capitella.
Eoobolus: Prominent extension of dorsal visceral platform (Balthasar 2009T).
Heliomedusa orienta: Corresponding to the “neck” of the vase-shaped visceral cavity reported by Zhang et al. 2009.
Lingulellotreta malongensis: An anterior projection of the visceral area is noted by Williams et al. (2000) and considered equivalent to that observed in Lingulosacculus (Balthasar & Butterfield 2009E).
Lingulosacculus: The prominent anterior extension of the visceral area noted by Balthasar & Butterfield (2009E) is considered as potentially homologous with that of Heliomedusa (Zhang et al. 2009) and, by extension, Haplophrentis (Moysiuk et al. 2017).
Sipunculus: Eversible pharynx (introvert).
Yuganotheca elegans: Possibly present, following interpretation of mouth (see fig. 2c, d in Zhang et al. 2014).
[85] Oesophageal folds
Character 85: Digestive tract: Oesophageal folds
Following character 86 in Giribet & Wheeler (2002).
Phoronis: Ciliated ridge in oesophagus (Torrey, 1901).
Character 89: Digestive tract: Midgut: Subdivisions
The molluscan midgut is functionally subdivided into a sorting area (stomach), digestion area (midgut sac or gland), and transport tube (intestine). Characters 42 in Haszprunar (2000), 1.38 in von Salvini-Plawen & Steiner (1996).
Canadia spinosa: The gut is a straight tube with no obvious subdivision (Parry & Caron, 2019).
Odontogriphus omalus, Wiwaxia corrugata: Subdivided, presumably functionally, but with some ambiguity [1;Smith2014].
[90] Glands
Character 90: Digestive tract: Midgut: Glands
Characters 1.40, 2.30 and 4.59 in von Salvini-Plawen & Steiner (1996); 42 in Haszprunar (2000).
Odontogriphus omalus, Wiwaxia corrugata: Annex to midgut interpreted as a gland (Smith, 2012b).
4.12 Digestive tract: Anus
[91] Presence
Character 91: Digestive tract: Anus: Presence
The digestive tract may either constitute a blind sac, or a through gut with anus. The loss of an anus is known to be derived within spiralia, so this character is treated as neomorphic.
Glyptoria: Scored according to familial level feature.
Kulindroplax perissokomos: Interpreted as possessing a through gut.
Kutorgina chengjiangensis: Although “the possibility of a blind ending may not be completely eliminated […] the weight of evidence […] leads us to reject the possibility of a blind-ending intestine” – Zhang et al. 2007R, p. 1399.
[92] Location
Character 92: Digestive tract: Anus: Location
“The relative position of the mouth and anus in the larvae of brachiopods and phoronids is similar: posterior anus and anterior mouth” – Williams et al. 2007, p. 2884
See also character 6 in Haszprunar & Wanninger (2008).
Chaetoderma: Coded as ambiguous (straight / rear of pedal sole) as the pedal sole is secondarily lost in the group.
Dentalium: The U-shaped gut of scaphopods arises by exaggeration of the dorsal surface, rather than migration of the anus (Steiner, 1992).
Kutorgina chengjiangensis: “Five specimens have an exceptionally preserved digestive tract, dorsally curved, with a putative dorso-terminal anus located near the proximal end of a pedicle” – Zhang et al. 2007R.
Terebratulina: “In rhynchonelliforms, the gut curves somewhat into a C-shape and the (blind) anus becomes posteroventral in position.” – Williams et al. 2007, p.
2884.
[93] Migration: Within ring of tentacles
Character 93: Digestive tract: Anus: Migration: Within ring of tentacles
A migrated anus may be located laterally or within the lophophore ring (as in entoprocts).
Kutorgina chengjiangensis: “Presumed to terminate in a functional anus located near the proximal end of the pedicle.” – Zhang et al. 2007R.
[94] Migration: Position
Character 94: Digestive tract: Anus: Migration: Position
If the anus is not within the ring of tentacles, in which direction is it oriented?
Flustra, Amathia: Anus remains on ventral surface. Arguably, rather than the anus migrating, the dorsal surface of the animal has become extended.
Dentalium: An alternative interpretation would be that the posterior of the scaphopod has been extended to generate the relatively anterior position of the originally ventral anus.
Haplophrentis carinatus: Opening to the right – see figures 1, 3, and extended data 5 in Moysiuk et al. (2017). The text states in error that the anus is to the left of the midline.
Kutorgina chengjiangensis: “Five specimens have an exceptionally preserved digestive tract, dorsally curved, with a putative dorso-terminal anus located near the proximal end of a pedicle” – Zhang et al. 2007R.
Lingula: “In the lingulids, the [intestine] follows an oblique course anteriorly to open at the anus on the right body wall.” – Williams et al. 1997, p. 89.
Lingulellotreta malongensis: “finally terminating in an anal opening on the right anterior body wall” (Zhang et al. 2007N, p.66).
Lingulosacculus: “This same arrangement occurs in L. nuda, with the looped dark line tracking the same course as the exceptionally preserved guts of Chengjiang lingulellotretids, including the median position of its posterior loop and the sharp right turn as it exits the posterior extension of the ventral valve” (Balthasar & Butterfield 2009E, p.310).
Longtancunella chengjiangensis: “The intestine extends posteriorly, and then turns right to continue as a tortuous strand, finally terminating at the latero-median position of the anterior body wall” – Zhang et al. 2007A.
Terebratulina: “In rhynchonelliforms, the gut curves somewhat into a C-shape and the (blind) anus becomes posteroventral in position.” – Williams et al. 2007, p.
2884.
Yuganotheca elegans: The identification of the “very poorly impressed possible anus at the lateral side of the anterior body wall” is not yet confident, so this character is coded as not presently available.
4.13 Sclerites
[95] Present in adult
Character 95: Sclerites: Present in adult
Plate-like (wider than tall) skeletal elements, whether mineralized or non-mineralized. Corresponds to character 8 in Vinther et al. (2017).
The definition deliberately excludes setae (which are taller than wide).
Tonicella, Dentalium: Molluscan valves are treated as potential homologues of brachiopod valves.
Halkieria evangelista: Halkieriid sclerites are interpreted as potentially homologous with those of Dailyatia and hence the brachiopods (Zhao et al., 2017).
Namacalathus: The mineralized endoskeleton of Namacalathus is not interpreted as a sclerite.
Serpula: Annelid setae are not considered to represent potential homologues with the brachiopod shell.
Sipunculus: Hooks are present, though the absence of chitin or microvillar impressions indicates that they are not homologous with those of other lophotrochozoans.
Wiwaxia corrugata: The scales of Wiwaxia are treated as homologous with the chaetae of annelids and brachiopods (Butterfield, 1990; Smith, 2014; Zhang et al., 2015), rather than brachiopod shell.
Yilingia spiciformis: The plate-like structures on the dorsal surface of Yilingia(Chen et al., 2019) are plausibly interpreted as non-mineralized sclerites.
[96] Periodically shed and replaced
Character 96: Sclerites: Periodically shed and replaced
Certain taxa periodically slough and replace some of their individual sclerites during growth. Others continue to add to sclerites by marginal accretion throughout life.
Acaenoplax hayae: Valves grown by marginal accretion (???).
Orthrozanclus: Inferred by comparison with Halkieria.
Paterimitra: Larval shell present at tip of sclerites (???), indicating retention.
Siphogonuchites multa: Retained as set in shell matrix (Bengtson, 1992).
Yilingia spiciformis: The broad size and interlocking nature of sclerites suggests that they are not periodically shed and replaced, consistent with the absence of any specimens lacking sclerites.
[97] Prominent major valves
Character 97: Sclerites: Prominent major valves
Equivalent to “Sclerites: Bivalved” in H.-J. Sun et al. (2018), rephrased to reflect the variation in the number of conceivably homologous ‘major’ shell plates in Aculifera.
A differentiated ventral or posterior valve may be present in addition to a prominent anterior/dorsal valve, corresponding to the ‘head valve’ of chitons or the dorsal valve of brachiopods.
Tonicella: As larvae, polyplacophorans exhibit an anterior and a posterior shell field (Wanninger & Haszprunar, 2002a); subsequent subdivision of the posterior field gives rise to the posterior seven valves. Tonicella is thus tentatively coded as ‘bivalved’ to reflect the potential (if perhaps unlikely) homology with the paired elements of brachiopods.
[98] Reduced
Character 98: Sclerites: Accessory sclerites: Reduced
Taxa in the bivalved condition may retain sclerites as small additional elements, such as the L-elements of Paterimitra (Skovsted et al. 2015). Hyolithid helens are coded as potentially homologous to these elements (following Moysiuk et al., 2017).
This character is treated as neomorphic, with accessory sclerites ancestrally present, recognizing the likely origin of brachiozoans (and Lophotrochozoans more generally) from a scleritomous organism.
Acaenoplax hayae, Kulindroplax perissokomos: The spines are interpreted as homologous with the girdle elements of polyplacophorans, i.e. as setae.
Cupitheca holocyclata: Helens never observed and considered absent (Skovsted et al., 2016).
Dentalium: The scaphopod valve arises posterior of the prototroch and is thus homologous with the posterior valves of Chiton, assuming that molluscan shell fields are homologous features.
Paramicrocornus: Helens absent, with no possible insertion point (Z.-L. Zhang et al., 2018).
Paterimitra: L-sclerites (Skovsted et al. 2009T).
Polysacos vickersianum: The annulus of spines is considered to represent accessory sclerites homologous to the main valves; see discussion under ‘adult setae’.
Siphogonuchites multa: It is possible that two shell morphs exist and belonged to the same individuals; or that other aggregations of spicules represent additional shell fields (Bengtson, 1992; Conway Morris & Chapman, 1996).
Tonicella: The intermediate shell plates arise by subdivision of the posterior shell field (Wanninger & Haszprunar, 2002a), and are thus treated as equivalent to the posterior valve rather than as distinct elements.
The girdle elements are homologous with annelid chaetae / brachiopod setae (Leise & Cloney, 1982), rather than sclerites.
[99] Arrangement
Character 99: Sclerites: Accessory sclerites: Arrangement
Following Zhao et al. (2017), and reflecting character 5 in Vinther et al. (2017).
Dailyatia: Following the reconstruction of Skovsted, Betts, Topper, & Brock (2015).
Yilingia spiciformis: Distinct dorsal and dorsolateral fields, albeit in phase (Chen et al., 2019).
[100] Symmetry
Character 100: Sclerites: Accessory sclerites: Symmetry
Yilingia spiciformis: Seemingly convex in thin section (Chen et al., 2019).
[102] Additional major valves
Character 102: Sclerites: Prominent major valves: Additional major valves
To reflect the single valve present in Orthrozanclus and the conceivable homology between the tail valve of Halkieria and the ventral valve of brachiopods.
Acaenoplax hayae: Eight valves, including V7v and V7d as separate valves.
Dailyatia: Absent – coded as lacking a prominent dorsal valve.
Paterimitra: The S2 sclerite (???) is treated as a prominent valve by virtue of its close affiliation with the S1 sclerite.
Pojetaia runnegari: The two valves are considered to be a single valve, separated along the midline and joined by the ligament, following the conventional interpretation of rostroconchs.
Yilingia spiciformis: No major valves (Chen et al., 2019).
[103] Additional valves: Nature
Character 103: Sclerites: Prominent major valves: Additional valves: Nature
The ventral valve of brachiopods is unlikely to be equivalent to the tail valve of Halkieria or chitons.
Paterimitra: The S2 valve is treated as ventral valve as it is associated with a likely pedicle opening.
[104] Serially repeated
Character 104: Sclerites: Posterior valves: Serially repeated
[105] Number
Character 105: Sclerites: Posterior valves: Number
Vinther et al. (2017) (character 19) report five intermediate shell fields in Kulindroplax, Acaenoplax, multiplacophorans, and the larvae of Chaetoderma.
Acaenoplax hayae: Seven, counting V7d as separate from V7v (???).
Kulindroplax perissokomos: Sharp jugal angle but no ridge.
[108] Insertion plates
Character 108: Sclerites: Posterior valves: Insertion plates
Character 32 in Vinther et al. (2017)
“In the majority of recent chitons the articulamentum may form extensions beyond the margin of the tegmentum. These extensions, called insertion plates, occur on the lateral margins of intermediate valves, on the anterior margin of the head valve and posteriorly on the tail valve” (Schwabe, 2010).
Acaenoplax hayae: (???).
Glaphurochiton carbonarius: Following Vinther et al. (2017).
Polysacos vickersianum: Present in multiplacophorans (Vinther et al., 2017).
Character 109: Sclerites: Posterior valves: Insertion plates: Slit
Character 33 in Vinther et al. (2017).
“The distal edge of the insertion plates may be slitted or solid in different taxa. The bridges between the slits (or incisions) are called teeth and may either be smooth at their outside, roughened, or even strongly pectinate.” (Schwabe, 2010).
Mopalia: (???).
Polysacos vickersianum: Following Vinther et al. (2017).
Tonicella: Slits with slit rays (Connors et al., 2012).
[110] Insertion plates: Slit: Nature
Character 110: Sclerites: Posterior valves: Insertion plates: Slit: Nature
Character 112: Sclerites: Posterior valves: Differentiated intermediate shell fields
Following character 17 in Vinther et al. (2017), itself derived from character 7 in (???). A satisfactory definition for this character is not available; it is here taken to mean “intermediate shell fields are differentiated from one another”, rather than “differentiated from the head/tail valves” or “spatially non-overlapping”.
Acaenoplax hayae: (???).
Glaphurochiton carbonarius: Following Vinther et al. (2017).
Kutorgina chengjiangensis: Williams et al. (1998b) (appendix 2) and Williams et al. (2000) (p. 208) consider the hinge of Kutorgina to be stropic, whereas Bassett et al (2001) argue for an astropic interpretation – whilst noting that the arrangement is prominently different from other astrophic taxa. We therefore code this taxon as ambiguous.
Longtancunella chengjiangensis: “Longtancunella has an oval to subcircular shell with a very short strophic hinge line” – Zhang et al. 2011T.
Micrina: Non-strophic: see Holmer et al 2008.
Nisusia sulcata: “The strophic, articulated shells of the Kutorginata rotated on simple hinge mechanisms that are different from those of other rhynchonelliforms” (Williams et al. 2000, p. 208).
Novocrania: Craniides have a strophic posterior valve edge (Williams et al. 2007, table 39 on p. 2853): Novocrania’s “dorsal posterior margin” is “straight” (Williams et al. 2000, p. 171).
Salanygolina: Coded as strophic in Williams et al (1998T); see Holmer, Pettersson Stolk, Skovsted, Balthasar, & Popov (2009).
Tomteluva perturbata: “Tomteluvid taxa all have a strongly ventribiconvex, astrophic shell with a unisulcate commissure” – Streng et al. 2016, p5.
Tonicella: A linear hinge articulation does not exist between valves 1 and 2; nor would it exist between valves 1 and 8 were these adjacent (Connors et al., 2012).
Yuganotheca elegans: Not evident from fossil material; the possibility of a short strophic hinge line (as in Longtancunella) is difficult to discount.
[115] Enclosing filtration chamber
Character 115: Sclerites: Bivalved: Enclosing filtration chamber
In crown-group brachiopods, the two primary shells close to form an enclosed filtration chamber. Further down the stem, taxa such as Micrina do not.
[116] Commissure: Exact correspondence of valve margins
Character 116: Sclerites: Bivalved: Commissure: Exact correspondence of valve margins
Orthothecid hyoliths can retract their operculum into their conical shell, in contrast to most other taxa, where the valves align exactly when they are closed, save perhaps for a pedicle notch or, in the case of hyolithids, depressions that allow the helens to protrude. Refers only to two prominent valves, not to additional sclerites of e.g. Eccentrothca.
Bactrotheca: Operculum interpreted as sitting inside conical shell (Marek, 1976).
Cupitheca holocyclata: “The width range of opercula matches that of the apertures” (H.-J. Sun et al., 2018), but it is not possible to determine whether this is an exact match or whether the operculum may have been slightly smaller, and hence retractable, as anticipated for orthothecids.
Paramicrocornus: Articulated specimens unknown.
[117] Commissure: Sulcate
Character 117: Sclerites: Bivalved: Commissure: Sulcate
The anterior commissure can be rectimarginate (i.e. straight), uniplicate (i.e. median sulcus in ventral valve), or sulcate (with median sulcus in dorsal valve).
Askepasma toddense: Coded as rectimarginate in Williams et al. (1998b), though note that the “ventral valve weakly to moderately sulcate” (Topper et al. 2013T); a similar description is provided by Williams et al. (2000). Coded as ambiguous for these two states accordingly.
Micromitra, Glyptoria, Kutorgina chengjiangensis, Salanygolina: Following appendix 2 in Williams et al. (1998T).
Terebratulina: “Anterior commissure rectimarginate to uniplicate” – uniplicate in fig. 1425.1c of Williams et al. (2006).
[118] Commissure: Circular
Character 118: Sclerites: Bivalved: Commissure: Circular
Shape of the commissure in plan view, ignoring any deflection arising due to articulation at the hinge (e.g. delthyrium/notothyrium). This character seeks to discriminate the essentially conical ‘conchs’ of orthothecid hyoliths from the polygonal ‘conchs’ of hyolithids. Triangular and oblong outlines are not distinguished, as this is not entirely independent of the strophic/astrophic nature of the hinge.
Kutorgina chengjiangensis: Lateral margins subparallel (Williams et al., 2000, fig. 125); clear angular corners in K. chengjiangensis(Holmer et al., 2018b).
Lingulellotreta malongensis: Linear, diverging lateral margins (Zhang et al., 2007a).
Ussunia: Essentially round, hinge notwithstanding (Williams et al., 2000).
Yuganotheca elegans: Polygonal (Zhang et al., 2014).
[119] Commissure: Lateral margins
Character 119: Sclerites: Bivalved: Commissure: Lateral margins
If lateral margins are linear, are the subparallel (i.e. commissure profile oblong, with long hinge) or diverging (i.e. commissure profile triangular, with short hinge)?
[120] Apophyses
Character 120: Sclerites: Bivalved: Apophyses
Micrina, like many brachiopods, bears tooth-like structures or processes that articulate the two primary valves. Caution must be applied before taxa are coded as “absent”, as teeth can be subtle and may be overlooked.
Alisina: “Strophic articulation with paired, ventral denticles, composed of secondary shell” – definition of family Trematobolidae in Williams et al. 2000.
Clupeafumosus socialis: No articulating processes evident or reported by Topper et al. (2013R).
Gasconsia: “Articulatory structure comprising ventral cardinal socket and dorsal hinge plate […] The shape of the shell probably correlates strongly with the unique type of articulation, which consists of a dorsal hinge plate that fits tightly into a cardinal socket in the ventral valve, with a concave homeodeltidium in the center of the ventral interarea” – Williams et al. 2000, p.184, concerning order Trimerellida.
Kutorgina chengjiangensis, Nisusia sulcata: Kutorginata don’t have teeth or dental sockets, but their shells are articulated by “two triangular plates formed by dorsal interarea, bearing oblique ridges on the inner sides” (Williams et al 2000, p. 211); this simple hinge mechanism is different from other rhynchonelliforms (Williams et al. 2000, p.208), but serves an equivalent purpose and is thus potentially homologous. We thus code kutorginids as present, using a subsequent character to capture difference in tooth morphology.
Mickwitzia muralensis: Not reported by or evident in Balthasar (2004).
Mummpikia nuda: No articulation structures are evident; instead, the propareas are rotated inwards (Balthasar 2008). The definition of Family Obolellidae in Williams et al. (2000) notes that articulation may be lacking or vestigial in the group.
Tomteluva perturbata: Tomteluvids […] lack articulation structures such as teeth and sockets (Streng et al. 2016).
Tonicella: The sutural laminae correspond in function and position to brachiopod apophyses (Connors et al., 2012), and so are coded as potentially homologous.
Ussunia: “articulatory structures poorly developed” – Williams et al. 2000, p. 192.
[121] Apophyses: Morphology
Character 121: Sclerites: Bivalved: Apophyses: Morphology
Deltidiodont teeth are simple hinge teeth developed by the distal accretion of secondary shell; Cyrtomatodont teeth are knoblike or hook-shaped hinge teeth developed by differential secretion and resorption of the secondary shell (fig. 322 in Williams et al 1997).
Kutorginata (here represented by Kutorgina and Nisusia) don’t have teeth (apophyses) or dental sockets, but their shells are articulated by “two triangular plates formed by dorsal interarea, bearing oblique ridges on the inner sides” (Williams et al 2000, p. 211); this simple hinge mechanism is different from other rhynchonelliforms (Williams et al. 2000, p.208; table 13 character 30), and is described as a “pseudodont articulation” (Holmer et al. 2018E).
Antigonambonites planus, Glyptoria: Coded as deltidiodont in Benedetto (2009).
Kutorgina chengjiangensis: “Articulation characterized by two triangular plates formed by dorsal interarea, bearing oblique ridges on the inner sides” – Williams et al 2000, p. 211.
Micrina: The simple knob-like teeth of Micrina show no evidence of resprobtion or the hook-like shape that characterises Cyrtomatodont teeth.
Nisusia sulcata: The ‘teeth’ are formed by the distal lateral extensions from the ventral
pseudodeltidium fitting into the ‘sockets’ on the inner side of the dorsal interarea (Holmer et al. 2018E). (Coded as “deltidiodont teeth absent” in Benedetto (2009).).
Orthis: Coded as deltidiodont (in Eoorthis) in Benedetto (2009).
Terebratulina: Cyrtomatodont – see fig. 322 in Williams et al (2000).
Tonicella: Chiton apophyses (sutural laminae) are accretions deriving from the ventral shell layer of the intermediate and tail valves (Schwabe, 2010), so correspond to the deltidiodont situation in brachiopods.
[122] Apophyses: Dental plates
Character 122: Sclerites: Bivalved: Apophyses: Dental plates
Williams et al. 1997 (p362) write: “Teeth […] are commonly supported by a pair of variably disposed plates also built up exclusively of secondary shell and known as dental plates (Fig. 323.1, 323.3).”
Dewing (2001) elaborates: “Dental plates are near-vertical, narrow sheets of shell tissue between the anteromedian edge of the teeth and floor of the ventral valve. They are a composite structure, resulting from the growth of teeth over the ridge that bounds the ventral-valve muscle field.”
Williams et al. 2000 (p.201) write: “The denticles lack supporting structures in all Obolellida, but in Naukatida they are supported by an arcuate plate below the
interarea, the anterise (Fig. 119.3a)”.
The anterise is conceivably homologous with the dental plates, thus the presence of either is coded “present” for this character.
Antigonambonites planus: Coded as present (well developed) in Benedetto (2009).
Coolinia pecten: Coded as present following Dewing (2001), who seems to use the term Strophomenoids to encompass Coolinia, and attests to the presence of dental plates.
Gasconsia: Coded ambiguous to reflect the possibility that the hinge plate in trimerellids is homologous to the dental plates of other taxa, and has replaced the teeth themselves as the primary articulatory mechanism (see Williams et al. 2000, p. 184, for details of the articulation).
Glyptoria, Nisusia sulcata: Coded as absent in Benedetto (2009).
Orthis: Coded as present (short and recessive, in Eoorthis) in Benedetto (2009).
[123] Sockets
Character 123: Sclerites: Bivalved: Sockets
Simplified from Bassett et al. (2001) character 16.
This character is independent of apophyses, as several taxa bear sockets without corresponding teeth; the function of these sockets is unknown.
See figs 323ff in Williams et al. (1997).
Alisina: “bearing sockets, bounded by low ridges” – Williams et al. 2000.
Antigonambonites planus: Coded as present in Benedetto (2009).
Gasconsia: “Articulatory structure comprising ventral cardinal socket and dorsal hinge plate” – Williams et al. 2000, p. 184.
Glyptoria, Nisusia sulcata: Coded as absent in Benedetto (2009).
Mickwitzia muralensis: Not reported by or evident in Balthasar (2004).
Tomteluva perturbata: Tomteluvids […] lack articulation structures such as teeth and sockets (Streng et al. 2016).
Ussunia: Following table 15 in Williams et al. 2000.
[124] Socket ridges
Character 124: Sclerites: Bivalved: Socket ridges
After Bassett et al. (2001) character 17. May be difficult to distinguish from a brachiophore (see Fig 323 in Williams et al 1997), so the two structures are not distinguished here.
Alisina: “bearing sockets, bounded by low ridges” – Williams et al. 2000.
Antigonambonites planus: Coded as present in Benedetto (2009).
Glyptoria, Nisusia sulcata: Coded as absent in Benedetto (2009).
Tomteluva perturbata: Tomteluvids […] lack articulation structures such as teeth and sockets (Streng et al. 2016).
[125] Muscle scars: Ventral
Character 125: Sclerites: Bivalved: Muscle scars: Ventral
After Bassett et al. (2001) character 6.
Alisina: Muscle scars scored based on Alisinacomleyensis (Bassett et al. 2001).
Bactrotheca: “Muscle scars were not found” – Valent, Fatka, Szabad, Micka, & Marek (2012).
Halkieria evangelista: Muscle scars are known from the Type A, but not Type B, morphs of the halkieriid Oikozetetes(Jacquet, Brock, & Paterson, 2014; Paterson, Brock, & Skovsted, 2009).
Alisina: Following reconstruction of Gorjansky & Popov (1986).
Askepasma toddense: Restricted to medial field, following the interpretation of the musculature presented by Williams et al. (2000), fig. 81.
Clupeafumosus socialis: Coded following Hadrotreta, as illustrated in Popov (1992).
Craniops: See fig. 89 in Williams et al. (2000).
Eoobolus: The ‘laterals’ of Balthasar (2009T, fig. 5) are situated almost upon the vasculalateralia; they are interpreted as sitting posterolateral to them.
Gasconsia: Musculature described in Hanken & Harper (1985), but location of mantle canals unknown.
Glyptoria: Posterolateral reflected by diductor attachments; see fig. 18.3.2 in Bassett et al. 2001.
Kutorgina chengjiangensis: Following situation in Nisusia; see fig. 18.2 in Bassett et al. (2001).
Lingulellotreta malongensis: See fig. 5 in Holmer et al. 1997E.
Micromitra: Posteriomedial muscle field (Williams et al. 1998T, text-fig. 6) treated as equivalent to posterolateral muscles.
Nisusia sulcata: Posterolateral diductors (fig. 18.2 in Bassett et al. 2001).
Orthis: Not applicable: vasculalateralia not comparable to those of other taxa.
Pelagodiscus atlanticus: Inapplicable as vascular system not directly equivalent to the canonical; see. fig 6b in Balthasar (2009T).
Salanygolina: Ventral musculature not clearly constrained (Holmer et al. 2009T).
Siphonobolus priscus: Coded following general siphonotretid condition described by Popov (1992, p. 407).
Ussunia: Internal anatomy not adequately preserved to evaluate (Nikitin & Popov, 1984).
[127] Muscle scars: Adjustor
Character 127: Sclerites: Bivalved: Muscle scars: Adjustor
After Bassett et al. (2001) character 7.
This character is contingent on the presence of a pedicle. Extreme caution must be used in inferring an absent state, as adjustor scars can be extremely difficult to distinguish from the adductor scars.
Alisina: Muscle scars scored based on Alisinacomleyensis (Bassett et al. 2001). The presence of an adjustor is marked as not presently available, as it is not clear that a scar, if present, could be distinguished from the diminutive muscle scars present.
Askepasma toddense: Following the interpretation of the musculature presented by Williams et al. (2000), fig. 81.
Botsfordia: Not described in Popov (1992).
Clupeafumosus socialis: Not known in any acrotretid (Williams et al. 2000); not evident in Clupeafumosus (Topper et al. 2013R).
Gasconsia: No mention of an adjustor muscle in Gasconsia or Trimerellida more generally on pp. 184–185 of Williams et al. 2000, nor in discussion in Williams et al. 2007 (p. 2850). Coded as absent.
Siphonobolus priscus: Ventral musculature poorly constrained (Williams et al. 2000; Popov et al. 2009).
[128] Muscle scars: Dorsal adductors
Character 128: Sclerites: Bivalved: Muscle scars: Dorsal adductors
After Bassett et al. (2001) character 8, and Williams et al. (1996, character 35; 2000, p. 160, character 54)
In the dorsal valve, the anterior and posterior adductor scars of articulated brachiopods form a single (quadripartite) muscle field (Williams et al. 2000, p. 201)
In contrast, the anterior and posterior scars of e.g. trimerellids have prominently separate attachment points, with anterior and posterior muscle fields clearly distinct, and coded as “dispersed”.
In e.g. kutorginates, adductor muscles are separated into left and right fields; the same is the case in lingulids, where there are more separate muscle groups and the left and right fields conspire to produce a radial arrangement; both of these configurations are scored as “radially arranged”.
Alisina: Following Williams et al. (2000) table 15 (their character 54).
Antigonambonites planus: Treatise.
Askepasma toddense: Separate left and right fields, so radially arranged – following the interpretation of the musculature presented by Williams et al. (2000), fig. 81.
Botsfordia: Following Williams et al. 1998T, appendix 2.
Clupeafumosus socialis: Following reconstruction of Hadrotreta by Williams (2000), fig. 51, which exhibits distinct left and right fields.
Gasconsia: Following the coding of Williams et al. (2000), table 15.
Glyptoria: Scored as “dispersed” by Williams et al. (1998T) … but then so is Kutorgina, which Bassett et al (2001) score as radial.
Williams et al. (2000) state, for superfamily Protorthida, “dorsal adductor scars probably linear”, which fits in the category of “radial” employed herein – so that’s what we follow.
Halkieria evangelista: It is unclear whether the paired muscle scars of Oikozetetes may be homologous to brachiopod adductors.
Haplophrentis carinatus: Moysiuk et al. (2017) reconstruct distinct left and right attachment scars, consistent with general situation in hyoliths (see Dzik 1980); it is unclear whether additional smaller scars were present in a radial arrangement (as in e.g. Gompholites, Marek, 1967) or whether unseen scars were dispersed, hence the partially ambiguous coding.
Heliomedusa orienta: Distinct anterior and posterior fields (Chen et al. 2007); coded as “dispersed” by Williams et al. (2000) in table 15.
Micromitra: Williams et al. (1998T) code as “dispersed”, but have a less divided scheme of character states and disagree with other sources in some codings (e.g. Bassett et al. 2001, in Kutorginates). Williams et al. (2000) do not describe Micromitra musculature and we were unable to find any reliable description of the scars, so we code as “not presently available”.
Novocrania: Craniids scored as “open, quadripartite” by Williams et al. (1996).
Pelagodiscus atlanticus: Discinids scored as “open, quadripartite” by Williams et al. (1996).
Salanygolina: “The dorsal valve of Salanygolina has a radial arrangement of adductor muscle scars and the scars of posteromedially placed internal oblique muscles, which are also characteristic of paterinates and chileates” – Holmer et al. (2009).
Siphonobolus priscus: Ventral musculature poorly constrained (Williams et al. 2000; Popov et al. 2009).
Terebratulina: Coded as “grouped, quadripartite” by Williams et al. (1996).
Ussunia: Following coding with state 0 (dispersed) in table 15 in Williams et al. 2000.
[129] Muscle scars: Adductors: Position
Character 129: Sclerites: Bivalved: Muscle scars: Adductors: Position
Position of adductor muscles relative to commissural plane.
After Bassett et al. (2001) character 11.
Askepasma toddense: Following the interpretation of the musculature presented by Williams et al. (2000), fig. 81.
Botsfordia: Following description of Popov (1992).
Coolinia pecten: Not reported by Williams et al. (2000), nor Bassett & Popov (2017), nor explicitly by Dewing (2001).
Eoobolus: “Eoobolus should have anterior and posterior adductors and a variety of oblique muscles which were probably arranged in criss-crossing pairs” – Balthasar 2009T.
Gasconsia: See discussion under Trimerellida in Williams et al. (2000).
Pelagodiscus atlanticus: Musculature considered essentially equivalent to Lingula by Williams et al 2000, so Lingula coding followed here.
Siphonobolus priscus: Ventral musculature poorly constrained (Williams et al. 2000; Popov et al. 2009).
[130] Muscle scars: Dermal muscles
Character 130: Sclerites: Bivalved: Muscle scars: Dermal muscles
Based on character 11 in Zhang et al. (2014).
Well developed dermal muscles present in the body wall of recent lingulates, which are absent in all calcareous-shelled brachiopods. These muscles are responsible for the hydraulic shell-opening mechanism, and possibly present in all organophosphatic-shelled brachiopods, with the possible exception of the paterinates (Williams et al., 2000, p. 32).
Alisina, Antigonambonites planus, Gasconsia, Glyptoria, Nisusia sulcata, Orthis, Salanygolina: According to the statement of Williams et al. (2000, p. 32) that these muscle are absent in all carbonate- shelled brachiopods.
Askepasma toddense: According to the statement of Williams et al. (2000, p. 32) that the presence of these muscles in paterinates is uncertain.
Botsfordia: Implicitly taken as present in Popov (1992), though not marked in diagrams – suggesting not strongly developed.
Clupeafumosus socialis: This character is coded based on the score of Acrotreta in Zhang et al. (2014), and statement in Williams et al. (2000, P.32).
Coolinia pecten: According to the statement of Williams et al. (2000, p. 32) that these muscle are absent in all carbonate-shelled brachiopods.
Eoobolus: Not remarked upon by Balthasar (2009T).
Kutorgina chengjiangensis: According to the statement of Williams et al. (2000, p. 32) that these muscle are absent in all carbonate- shelled brachiopods, and the coding for kutorginids in Zhang et al. (2014).
Micromitra: Williams et al. (2000, p. 32) are uncertain about the presence of these muscles in the paterinates. Zhang et al. (2014) code absence in Paterinida, but without specifying evidence; we follow their coding here.
Mummpikia nuda, Tomteluva perturbata: Though Williams et al. (2000, p. 32) state that these muscles are absent in all carbonate-shelled brachiopods, their existence cannot be discounted with certainty in this taxon, which is therefore coded not presently available.
Novocrania: Following Zhang et al. (2014), and the statement of Williams et al. (2000) that such muscles are absent in all calcite-shelled brachiopods.
Pelagodiscus atlanticus: Musculature considered essentially equivalent to Lingula by Williams et al 2000, so Lingula coding followed here.
Siphonobolus priscus: Ventral musculature poorly constrained (Williams et al. 2000; Popov et al. 2009).
Terebratulina: Williams et al. (2000, p. 32) state that these muscles are absent in all carbonate-shelled brachiopods.
[131] Muscle scars: Unpaired median (levator ani)
Character 131: Sclerites: Bivalved: Muscle scars: Unpaired median (levator ani)
The levator ani is a diminutive unpaired medial muscle found in certain calcitic brachiopods (Williams et al. 2000; see fig. 89, character 34 in table 13).
Alisina, Kutorgina chengjiangensis, Nisusia sulcata: Following table 13 in Williams et al. 2000.
Coolinia pecten: Not reported in Dewing (2001).
Craniops: See fig. 90 in Williams et al. 2000.
Gasconsia: Williams et al. 2000 code an unpaired medial muscle scar as present in their table 13, but give no reference for this coding, which perhaps arises from their interpretation of the taxon as a trimerellid. Hanken and Harper (1985, p. 249 and text-fig. 2) explicitly identify a pair of central muscles, so we code a levator ani as absent.
Heliomedusa orienta: Poor preservation of minor muscle scars noted by Chen et al. (2007).
Novocrania: Following table 13 in Williams et al. 2000 (for Novocrania).
Pelagodiscus atlanticus: Musculature considered essentially equivalent to Lingula by Williams et al 2000, so Lingula coding followed here.
Siphonobolus priscus: Ventral musculature poorly constrained (Williams et al. 2000; Popov et al. 2009).
Ussunia: Following table 15 in Williams et al. 2000.
[132] Muscle scars: Dorsal diductor
Character 132: Sclerites: Bivalved: Muscle scars: Dorsal diductor
After Bassett et al. (2001) character 9.
Acanthotretella spinosa: Not observable in Acanthotretella itself, so coded as ambiguous – though it is likely based on the anticipated phylogenetic affinities of Acanthotretella that the muscles are absent.
Askepasma toddense: Possible diductor scar could instead correspond to discinoid posterior adductors (Williams et al., 1998b); coded as uncertain. Not reconstructed in the the interpretation of the musculature presented by Williams et al. (2000), fig. 81.
Clupeafumosus socialis: Not reported by Topper et al. (2013R), nor reconstructed in generic acrotretid by Williams et al. (2000).
Gasconsia: Internal oblique muscles serve as diductors.
Halkieria evangelista: It is unclear whether the paired muscle scars of Oikozetetes are homologous to brachiopod diductors.
Micromitra: Possible diductor scar could instead correspond to discinoid posterior adductors (Williams et al., 1998b); coded as uncertain.
Siphonobolus priscus: Ventral musculature poorly constrained (Williams et al. 2000; Popov et al. 2009).
Ussunia: Internal oblique muscles present (Nikitin & Popov, 1984) and taken to serve as diductors by analogy with Gasconsia.
[133] Muscle scars: Dorsal diductor: Position
Character 133: Sclerites: Bivalved: Muscle scars: Dorsal diductor: Position
After Bassett et al. (2001) character 10.
Siphonobolus priscus: Ventral musculature poorly constrained (Williams et al. 2000; Popov et al. 2009).
4.14 Sclerites: Dorsal valve
[134] Growth direction
Character 134: Sclerites: Dorsal valve: Growth direction
See Fig. 284 in Williams et al (1997).
The growth direction dictates the attitude of the cardinal area relative to the hinge, which does not therefore represent an independent character.
Crudely put, if, viewed from a dorsal position, the umbo falls within the outer margin of the shell, growth is holoperipheral; if it falls outside the margin, it is mixoperipheral; if it falls exactly on the margin, it is hemiperipheral.
Acaenoplax hayae: Holoperipheral (???).
Calvapilosa kroegeri: Umbo in centre of valve (Vinther et al., 2017).
Clupeafumosus socialis: Appears hemiperipheral in fig. 3 in Topper et al (2013R), though bordering on holoperipheral, so scored as ambiguous.
Craniops: “Both valves with growth holoperipheral” – Williams et al. 2000, p. 164.
Tonicella: For the purposes of this analysis, we must treat polyplacophoran and brachiopod valves as potentially homologous.
In brachiopods, the dorsal valve bears the lophophore, which arises from the anterior lobe of the larva (Altenburger et al., 2013) – indicating that the dorsal shell field is associated with the anterior lobe.
In polyplacophorans, the head valve arises from a shell field on the anterior (pre-prototroch) lobe of the larva (Wanninger & Haszprunar, 2002a), which we therefore treat as homologous with the brachiopod dorsal valve.
In support of this hypothesis, we note that the posterior (but not anterior) valves of chitons bear apophyses (Connors et al., 2012; Schwabe, 2010), which are most prominent in the ventral (but not dorsal) valves of brachiopods (Williams et al 1997, fig. 322), and which occur in the morph A shell of Oikozetetes, which is interpreted as the posterior valve of a halkieriid (Paterson et al., 2009).
As the single posterior shell field of polyplacophorans subdivides to give rise to the six intermediate valves plus the tail valve (Wanninger & Haszprunar, 2002a), we prefer to consider the intermediate valves as representing “subdivisions” of a single valve rather than additional valves added to the body plan.
Growth is hemiperipheral in the anterior valve of polyplacophorans and holoperipheral in the posterior valves (Connors et al., 2012; Schwabe, 2010).
Ussunia: Growth “mixoperipheral in both valves” in trimerellids (Popov, Holmer, & Gorjansky, 1997; Williams et al., 2000).
[135] Aspect
Character 135: Sclerites: Dorsal valve: Aspect
Length:width ratio of the primary valve. Coded ambiguous in marginal cases: for example, a length:width ratio of 1.02:1 might be coded ambiguous(elongate, equant).
Acaenoplax hayae: Equant (???).
Calvapilosa kroegeri: Slightly longer than wide (Vinther et al., 2017).
Glaphurochiton carbonarius: Described as “semi-circular to elongate”, but some figured material is almost wider than long (Hoare & Mapes, 1986); coded as equant to transverse.
Halkieria evangelista: Approximately equant (???).
Kulindroplax perissokomos: Wider than long (Sutton et al., 2012).
Character 136: Sclerites: Dorsal valve: Posterior surface: Differentiated
In shells that grow by mixoperipheral growth, the triangular area subtended between each apex and the posterior ends of the lateral margins is termed the cardinal area. In shells with holoperipheral growth, a flattened surface on the posterior margin of the valve is termed a pseudointerarea (paraphrasing Williams et al. 1997).
In order for this character to be independent of a shell’s growth direction, we do not distinguish between a “cardinal area”, “interarea” or “pseudointerarea”.
Acaenoplax hayae: Not differentiated; essentially round (???).
Acanthotretella spinosa: Pseudointerarea present, following Siphonotretidae coding in Williams et al. (2000), table 6.
Askepasma toddense: Well-defined pseudointerarea (Williams et al. 2000, p153).
Botsfordia: “dorsal pseudointerarea vestigial, divided by median groove” – Williams et al. 2000.
Calvapilosa kroegeri: Slight concavity of posterior surface (Vinther et al., 2017).
Clupeafumosus socialis: Pseudointerarea present; figured by Topper et al. (2013R), fig. 3j.
Craniops: “Only some craniopsids (Lingulapholis, Pseudopholidops [not Craniops]) have well-developed pseudointerareas.” – Williams et al. 2000.
Gasconsia: Absent: the dorsal (branchial) pseudointerarea of G. schucherti is “reduced or obsolete”; that of G. worsleyi “short, virtually obsolete” (Hanken & Harper 1985).
Haplophrentis carinatus: A very short pseudointerarea appears to be present (Moysiuk et al. 2017).
Heliomedusa orienta: Pseudointerea in ventral valve, but not dorsal valve (Williams et al. 2000, 2007).
Leptochiton: (???).
Lingula, Lingulellotreta malongensis: Pseudointerarea present, following Williams et al. (2000), table 6.
Lingulosacculus: Unclear from fossil material.
Longtancunella chengjiangensis: Zhang et al. (2011T) note that “all evidence of a pseudointerarea is lacking”, but the two-dimensional preservation style of Chengjiang material makes details of dorsal valve difficult to distinguish, and the possibility of a diminutive pseudointerarea cannot be excluded with total confidence.
Mickwitzia muralensis: Shell flat.
Micrina: = Sellate sclerite duplicature (Holmer et al. 2008).
Micromitra: “Dorsal pseudointerarea usually well defined, low, anacline to catacline” – Williams et al. 2000.
Mummpikia nuda: “Information on the dorsal interarea is inconclusive […] no obvious
interarea is recognisable; whether or not this is the primary state or a taphonomic artefact is difficult to assess” – Balthasar 2008, p. 276.
Nisusia sulcata: Cardinal area (interarea) present – with reference to Holmer et al. (2018E).
Siphonobolus priscus: “Dorsal pseudointerarea weakly anacline, undivided, elevated above the valve floor” – Popov et al. 2009.
Terebratulina: Interarea present.
Tonicella: V-shaped notch in anterior valve (Schwabe, 2010).
Ussunia: Following table 15 in Williams et al. 2000.
Yuganotheca elegans: A differentiated region is not obvious in fossil material or its reconstruction (Zhang et al. 2014), but the two-dimensional preservation style of Chengjiang material makes details of dorsal valve difficult to distinguish, and the possibility of a diminutive pseudointerarea cannot be excluded with confidence.
Character 137: Sclerites: Dorsal valve: Differentiated posterior surface: Morphology
It is possible for a cardinal area or pseudointerarea to be distinct from the anterior part of the shell, yet to remain curved in lateral profile.
Taking an undifferentiated posterior margin as primitive, the primitive condition is curved – flattening of the posterior margin represents an additional modification that can only occur once the posterior margin is differentiated.
Bactrotheca: The short aspect of the cardinal interarea (Valent et al., 2012) makes it difficult to evaluate whether it is planar or curved.
Botsfordia: “Curved pseudointerarea” – Skovsted et al. 2017.
Calvapilosa kroegeri: Slight concavity of posterior surface (Vinther et al., 2017).
Clupeafumosus socialis: Truncated but essentially planar surface; see e.g. p196 of Topper et al. 2013R.
Cupitheca holocyclata: Curved (H.-J. Sun et al., 2018).
Eoobolus: Essentially planar; see Balthasar (2009T), fig. 4a.
Pelagodiscus atlanticus, Gasconsia, Heliomedusa orienta, Mickwitzia muralensis, Ussunia: Posterior surface cannot be flat if it is not differentiated.
Glaphurochiton carbonarius: Irregular but overall concave (Hoare & Mapes, 1986).
Micromitra: Essentially straight; see fig. 3.7 in Ushatinskaya 2016P.
Orthrozanclus: Posterior face appears close to planar (Conway Morris & Caron, 2007; Zhao et al., 2017).
Pedunculotheca diania: Difficult to evaluate based on present material, given low nature of valve and compressed preservation.
Siphonobolus priscus: The short interarea appears planar (see for example Popov et a. 2009 fig. 6A), but its short length makes it difficult to establish whether slight curvature is present.
Tonicella: Essentially planar, though open in aspect (following Chiton in Schwabe, 2010).
[138] Posterior surface: Medial groove
Character 138: Sclerites: Dorsal valve: Posterior surface: Medial groove
Following character 29 in Williams et al. (2000), table 9 (which relates to pseudointerarea).
Acanthotretella spinosa: The dorsal pseudointerarea is poorly preserved, but appears to have a median groove (Holmer & Caron, 2006).
Botsfordia: “dorsal pseudointerarea vestigial, divided by median groove” – Williams et al. 2000.
Clupeafumosus socialis: Present; figured by Topper et al. (2013R), fig. 3j.
Conocardium elongatum: Arguably the gap between the valves represents a medial groove.
Siphonobolus priscus: The dorsal pseudointerarea of S. priscus is undivided (Popov et al. 2009), but in other species it is divided by a “wide, poorly defined median groove” (Williams et al. 2000). Coded, therefore, as polymorphic.
[139] Posterior surface: Notothyrium
Character 139: Sclerites: Dorsal valve: Posterior surface: Notothyrium
A notothyrium is an opening in an interarea that accommodates the pedicle, and may be filled with plates.
Botsfordia: Following Williams et al. 1998T, appendix 2.
Longtancunella chengjiangensis: No evidence or report of an opening at the hinge line in fossil material in Zhang et al. 2007A or Zhang et al. 2011T.
Character 141: Sclerites: Dorsal valve: Posterior surface: Notothyrium: Chilidial plates
A notothyrium may be open or covered by a chilidium or two chilidial plates.
No included taxa exhibit more than one chilidial plate.
Transformational as it is not self-evident whether the ancestral taxon had an open or closed notothyrium.
[142] Notothyrial platform
Character 142: Sclerites: Dorsal valve: Notothyrial platform
After Bassett et al. (2001) character 12.
The presence or absence of a notothyrial platform, which often serves as an attachment point for the diductors in a similar fashion to the cardinal processes, is independent of the presence of a notothyrium.
Alisina, Glyptoria: Bassett et al. (2001) score as present in Table 18.1.
Askepasma toddense: Raised notothyrial platform (Williams et al., 1998b).
Coolinia pecten: Referred to as the “posterior platform” in Dewing (2001).
Kutorgina chengjiangensis: “Dorsal diductor scars impressed on floor of notothyrial cavity”: Williams et al. 2000, regarding Kutorginata.
Bassett et al. (2001) score as absent in Table 18.1.
Micromitra: A low notothyrial plate (Williams et al., 1998b) conceivably correspond to the raised notothyrial platform of Askepasma; coded ambiguous accordingly.
Nisusia sulcata: Bassett et al. (2001) score as absent in Table 18.1.
“Dorsal diductor scars impressed on floor of notothyrial cavity”: Williams et al. 2000, regarding Kutorginata.
Ussunia: “Visceral platforms absent in both valves” – Williams et al. 2000, p. 192.
[143] Medial septum
Character 143: Sclerites: Dorsal valve: Medial septum
The dorsal valve of many taxa is exhibits a septum or process (or myophragm) along the medial line. See character 25 in Benedetto (2009).
Acanthotretella spinosa: Not described by Holmer & Caron (2006), but an unannotated linear feature corresponds to the position of a median septum. Without detailed study of the specimen, we opt to score this as ambiguous.
Antigonambonites planus: Weakly developed septum evident in internal cast: Williams et al. 2000, fig. 508.2e.
Botsfordia: “dorsal interior with narrow anterior projection extending to midvalve, bisected by median ridge” – Williams et al. 2000.
Clupeafumosus socialis: Prominent process evident (Topper et al., 2013R).
Eoobolus: A “median projection” is present (fig. 4g in Balthasar 2009T).
Glyptoria: Neither evident nor reported in Williams et al. (2000).
Heliomedusa orienta: Reported on ‘ventral’ valve by Chen et al. (2007); we consider their ‘ventral’ valve to be the dorsal valve.
The structure is unambiguously figured (e.g. fig. 5.1 in Chen et al. 2007), contra its coding as absent in Williams et al. 2000 and its lack of mention in Williams et al. 2007 or Zhang et al. 2009.
Kutorgina chengjiangensis: Absent – fig. 129.1f in Williams et al. (2000).
Lingulellotreta malongensis: Very weakly developed but seemingly present between muscle scars in Lingulellotreta, more prominent in Aboriginella (also Lingulellotretidae) (Williams et al. 2000, fig. 34).
Lingulosacculus: It is not possible to determine, based on the material presented in Balthasar & Butterfield (2009E), whether the anterior projection of the visceral area in the dorsal valve corresponds to a medial septum in the underlying shell.
Mummpikia nuda: See pl. 2 panel 6 in Balthasar (2008).
Nisusia sulcata: Fig. 125 in Williams et al. (2000).
Novocrania: Median process evident: Williams et al. (2000) fig. 100.2a, d.
Orthis: Short medial process (“low median ridge”, p. 724) present in dorsal valve; see Fig. 523.3b in Williams et al. (2000).
Siphonobolus priscus: “Dorsal interior […] bisected by a short median ridge.” – Popov et al. 2009.
Ussunia: Following char 42 in table 15 in Williams et al. 2000.
[144] Cardinal shield
Character 144: Sclerites: Dorsal valve: Cardinal shield
The hyolithid operculum is divided into a cardinal and conical shield (Z.-L. Zhang et al., 2018), separated by furrows corresponding to the position of the helens. See Marek (1976) (fig. 2) or Martí Mus & Bergström (2005) (fig. 1) for schematic.
With no obvious sites for muscle attachment, the shields are unlikely to be homologous to the notothyrial platform.
Bactrotheca: No differentiation between the cardinal and conical shields.
Cupitheca holocyclata: Narrow cardinal shield (Skovsted et al., 2016).
Character 145: Sclerites: Dorsal valve: Cardinal processes
After Bassett et al. (2001) character 13. See Martí Mus & Bergström (2005) for an illustration.
Cardinal processes are unlikely to be homologous with the notothyrial platform, even if their function is similar.
Bactrotheca: “Narrow broadly diverging cardinal processes with subparallel edges” – Valent et al. (2012).
Clupeafumosus socialis: Not reported by Topper et al. (2013R).
Cupitheca holocyclata: Well-defined (Skovsted et al., 2016).
Longtancunella chengjiangensis: Not evident, and ought arguably to be discernable if present given the quality of preservation.
Paramicrocornus: Present (Z.-L. Zhang et al., 2018).
[146] Cardinal teeth
Character 146: Sclerites: Dorsal valve: Cardinal teeth
Radially arranged teeth, separated by furrows, adorn the cardinal margin of the operculum of certain hyolithids (Marek, 1963). The absence of corresponding tooth sockets indicates that they do not serve to articulate the valves; Marek (1967) does not consider the teeth to be homologous with brachiopod cardinal teeth.
[147] Clavicles
Character 147: Sclerites: Dorsal valve: Clavicles
Prominent symmetrical ridges on the inner surface of the hyolith operculum.
Cupitheca holocyclata: “No traces of clavicles” (Skovsted et al., 2016).
Character 148: Sclerites: Dorsal valve: Clavicles: Type of clavicles
Usually the operculum of hyoliths has one pair of clavicles, but in some taxa of hyolithida there are more than one pair of clavicles, which can be divided into six types (Marek, 1967). The included taxa either exhibit a single pair of monoclavicles, or three pairs of clavicles.
Character 149: Sclerites: Ventral valve: Growth direction
See Fig. 284 in Williams et al. (1997) for depiction of terms.
The growth direction dictates the attitude of the cardinal area relative to the hinge, which does not therefore represent an independent character.
Crudely put, if, viewed from a dorsal position, the umbo falls within the outer margin of the shell, growth is holoperipheral; if it falls outside the margin, it is mixoperipheral; if it falls exactly on the margin, it is hemiperipheral.
Clupeafumosus socialis: Inferred from Topper et al. (2013R).
Craniops: “Both valves with growth holoperipheral” – Williams et al. 2000, p. 164.
Heliomedusa orienta: Williams et al. (2000, 2007) reconstruct mixoperipheral growth in the ventral valve (though Chen et al. (2007) reconstruct the valves the other way round, i.e. it is the ventral valve that grows holoperipherally, and the dorsal mixoperipherally).
Paterimitra: The apical flange notwithstanding, the umbo of the S1 sclerite is posterior of the hinge line and the posterior edge of the lateral plate – see Larsson et al. 2014, fig. 2a, c.
Siphonobolus priscus: Initially holoperipheral (Popov et al. 2009, p. 159), then on the brink of being mixoperipheral in adulthood, so coded as polymorphic.
Tonicella: Growth is hemiperipheral in the anterior valve of polyplacophorans and holoperipheral in the posterior valves (Connors et al., 2012; Schwabe, 2010).
Ussunia: Growth “mixoperipheral in both valves” in trimerellids (Popov et al., 1997; Williams et al., 2000).
[150] Relative size
Character 150: Sclerites: Ventral valve: Relative size
In many brachiopods, the valves are closely similar in size; in others, the ventral valve is markedly larger than the dorsal, on account of being more convex. Marginal cases are treated as ambiguous for the relevant states.
Antigonambonites planus: Broadly equivalve – see Williams et al. (2000) fig. 508.2c.
Botsfordia: After table 8 in Williams et al. (2000).
Craniops: “Shell subequally biconvex” – Williams et al. 2000.
Eoobolus: “Eoobolus is biconvex”, but in his amended diagnosis, Balthasar (2009T) described it as “shell inequivalved, dorsibiconvex”.
Gasconsia: Equivalve as juveniles, becoming “convexiplane” (Williams et al. 2000, p. 187) as adults (Hanken & Harper, 1985).
Heliomedusa orienta: Ventral valve larger than the dorsal valve (Zhang et al. 2009, p. 659).
Kutorgina chengjiangensis: Ventral valve larger (see Williams et al. 2000, fig. 125.).
Leptochiton: Dorsal valve slightly larger (???).
Longtancunella chengjiangensis, Yuganotheca elegans: The ventral valve is somewhat, but not markedly, larger than the dorsal; as such, this character is coded ambiguous for equivalve/ventral valve larger.
Mummpikia nuda: Aside from hinge, valves similar in convexity and size (Balthasar 2008).
Nisusia sulcata: Ventral valve larger (see Williams et al. 2000, fig. 126.).
Siphonobolus priscus: Ventribiconvex (Popov et al. 2009).
Tonicella: Coded as ambiguous for equivalve/ventral valve larger: the posterior embryonic shell field, treated herein as equivalent to the ventral valve,.
Ussunia: Subequally biconvex (Williams et al. 2000, p. 192).
[151] Posterior surface: Differentiated
Character 151: Sclerites: Ventral valve: Posterior surface: Differentiated
In shells that grow by mixoperipheral growth, the triangular area subtended between each apex and the posterior ends of the lateral margins is termed the cardinal area. In shells with holoperipheral growth, a flattened surface on the posterior margin of the valve is termed a pseudointerarea (paraphrasing Williams et al. 1997).
In order for this character to be independent of a shell’s growth direction, we do not distinguish between a “cardinal area”, “interarea” or “pseudointerarea”.
Bactrotheca: No clear delineation of posterior (functionally dorsal) surface.
Clupeafumosus socialis: Described by Topper et al. (2013R).
Cupitheca holocyclata: No evidence of differentiation; circular cross-section (Vendrasco, Checa, & Porter, 2017).
Gasconsia: The region corresponding to the ventral (pseudo)interarea is described as a “trimerellid ventral cardinal area” by Williams et al. (2000, p.162), who code both an interarea and a pseudointerarea as absent in trimerellids.
Heliomedusa orienta: Zhang et al. (2009) report a moderate to somewhat developed ventral pseudointerarea, confirmed by Williams et al (2007).
Lingulosacculus: The conical valve is interpreted as the ventral valve with an extended pseudointerarea.
Longtancunella chengjiangensis: Though “all evidence of a pseudointerarea is lacking” – Zhang et al. 2011T – the region of the shell between the strophic hinge line and the colleplax (fig. 2 in Zhang et al. 2011T) is distinct from the rest of the shell; the ends of the strophic hinge line are marked by prominent nicks in the shell margin. Longtancunella is therefore coded as having a differentiated posterior surface.
Mickwitzia muralensis: Termed an interarea by Balthasar (2004).
Mopalia: (???).
Mummpikia nuda: Balthasar (2008) interprets a pseudointerarea as being present – e.g. p273, “Of particular interest is the vault that bridges the most anterior portion of the ventral pseudointerarea and raises it above the visceral platform.”; “This pattern is reversed in the ventral valves of M. nuda, where the anterior projection of the pedicle groove is raised above the valve floor whereas the lateral parts of pseudointerarea are not”.
Paterimitra: Triangular notch and subapical flange.
Pedunculotheca diania: Lateral lines suggest differentiation of posterior surface, but difficult to discern a change in morphology of this region. Coded ambiguous.
Siphonobolus priscus: “Ventral pseudointerarea, low, undivided, poorly defined” – Williams et al. 2000.
Terebratulina: Interarea.
Tonicella: Following the proposed homology model between the posterior valve of polyplacophorans and the ventral valve of brachiopods, the “posterior” surface of the polyplacophoran valve is taken to be the surface that would articulate with the anterior valve, which is anatomically anterior on the living organism.
Ussunia: Following char 17 in table 15 of Williams et al. 2000.
[152] Posterior margin growth direction
Character 152: Sclerites: Ventral valve: Posterior margin growth direction
Balthasar (2008) notes an inward-growing posterior margin of the pseudointerarea as potentially linking Mummpikia with the linguliform brachiopods.
Coded as inapplicable in taxa without a differentiated posterior margin: the posterior margin can only grow inwards if it is differentiated from the anterior margin; else the entire shell would grow in on itself.
Botsfordia: Inward-growing; see Skovsted & Holmer (2005), pl. 4.
Clupeafumosus socialis: See Topper et al. (2013R).
Eoobolus: See for example Skovsted & Holmer (2005), pl. 3.
Lingulellotreta malongensis: Transverse cross section of ventral pseudointerarea concave.
Mopalia: (???).
Mummpikia nuda: Balthasar (2008) interprets an inward-growing posterior margin of the pseudointerarea – e.g. p273, “Of particular interest is the vault that bridges the most anterior portion of the ventral pseudointerarea and raises it above the visceral platform […] An inward-growing posterior margin is otherwise known only from the pseudointerareas of linguliform brachiopods”.
[153] Posterior surface: Planar
Character 153: Sclerites: Ventral valve: Posterior surface: Planar
It is possible for a cardinal area or pseudointerarea to be distinct from the anterior part of the shell, yet to remain curved in lateral profile.
Taking an undifferentiated posterior margin as primitive, the primitive condition is curved – flattening of the posterior margin represents an additional modification that can only occur once the posterior margin is differentiated.
A flat and triangular interarea links Mummpikia with the Obolellidae (Balthasar 2008) – but all included taxa have triangular interareas, so this is not listed as a separate character.
Acanthotretella spinosa: ventral pseudointerareas are most similar to those found within the Order Siphonotretida.
Botsfordia: See Skovsted & Holmer (2005), pl. 3, fig. 14.
Clupeafumosus socialis: “Ventral pseudointerarea is gently procline and is flat in lateral profile”. —
(Topper et al. 2013R).
Eoobolus: Some curvature retained.
Haplophrentis carinatus: Dorsal surface essentially linear (Moysiuk et al., 2017, fig ed6a, ed7a).
Lingulellotreta malongensis: Transverse cross section of ventral pseudointerarea concave.
Longtancunella chengjiangensis: Flattened, reflecting the strophic hinge line.
Micromitra: Essentially planar; see fig. 6 in Ushatinskaya 2016P.
Mopalia: (???).
Paramicrocornus: Posterior (functionally dorsal) surface is linear in adults (though slightly curving in juveniles) (Z.-L. Zhang et al., 2018).
Pedunculotheca diania: Essentially linear.
Siphonobolus priscus: ‘Almost’ planar – see Popov et al. (2009, fig. 4). Coded as ambiguous.
Oh dear! You included the inapplicable token in a neomorphic character!
That’s unlikely to be a good idea: see Brazeau, Smith & Guillerme (2018, Systematic Biology).
Unless you are very sure that you understand the consequences, you should mark the character as Transformational by setting State 0 to [Transformational character], or re-code:
Acaenoplax_hayae
Kulindroplax_perissokomos
Phthipodochiton_thraivensis
Calvapilosa_kroegeri
Glaphurochiton_carbonarius
Polysacos_vickersianum
[154] Ligula
Character 154: Sclerites: Ventral valve: Ligula
The aperture of many hyolithid hyoliths is characterised by a ligula, a tongue-like protruding shelf on the functionally ventral surface of conical shell (Martí Mus & Bergström, 2005). This can be recognized by an acute angle in the lateral profile of the commissure (see second figure on p. 91 of Marek, 1966). No brachiopods display an equivalent feature.
Paramicrocornus: “Very short” semicircular ligula (Z.-L. Zhang et al., 2018).
[155] Posterior surface: Extent
Character 155: Sclerites: Ventral valve: Posterior surface: Extent
Distinguishes taxa whose ventral valve is essentially flat from those that are essentially conical.
Antigonambonites planus: Though scored High in data matrix of Benedetto (2009), this taxon (see Williams et al. 2000, fig. 508) does not express the deeply conical ventral valve that this character is intended to reflect. It is charitably coded as ambiguous.
Clupeafumosus socialis: Entire valve length – see schematic in Williams et al. (1997), fig. 286.
Coolinia pecten: See fig. 485 in Williams et al. 2000.
Gasconsia: “ventral cardinal interarea low, apsacline, with narrow, poorly defined homeodeltidium” – Williams et al. 2000, p. 186.
Kutorgina chengjiangensis: This taxon (see Williams et al. 2000, fig. 129; Popov 1992, fig. 1) comes close to expressing the deeply conical ventral valve that this character is intended to reflect, though this is not always so pronounced (e.g. Williams et al. 2000, fig. 125). It is therefore coded as ambiguous.
Mickwitzia muralensis: Often not prominently high (Skovsted & Holmer, 2003; Balthasar, 2004), though in some cases (e.g. Butler et al. 2015) the ventral valve approaches the conical shape that this character is intended to capture. Coded as polymorphic.
Nisusia sulcata: Scored as high in data matrix of Benedetto (2009), and depicted as such in Williams et al. (2000, fig. 125) and Popov (1992, fig. 1); but not high in all specimens (e.g. Williams et al. 2000, fig. 126). It is therefore coded as polymorphic.
Novocrania: Low cone.
Orthis: Scored ‘Low’ for Eoorthis by Benedetto (2009); assumed same in Orthis.
Salanygolina: Whereas Williams et al. (2000, p. 156) describe the ventral pseudointerarea as high, the shell lacks the deeply conical aspect that this character is intended to capture; we thus code the taxon as ambiguous.
[156] Posterior surface: Delthyrium
Character 156: Sclerites: Ventral valve: Posterior surface: Delthyrium
A delthyrium is an opening in an interarea or pseudointerarea that accommodates the pedicle, and may be filled with plates.
The homology of the pedicle in the pseudointerarea of obolellids and botsfordiids with the umbonal pedicle foramen of acrotretids was proposed by Popov (1992), and seemingly corroborated by observations of Ushatinskaya & Korovnikov (2016R), who note that the propareas of the Botsfordia ventral valve sometimes merge to form an elongate teardrop-shaped pedicle foramen.
Acanthotretella spinosa: Origin modelled on Siphonobolus.
Askepasma toddense: Homeodeltidium absent (Williams et al. 2000, p. 153); deltidium is open (see Topper et al. 2013T, fig. 4).
Botsfordia: The homology of the triangular notch or groove in the pseudointerarea with the umbonal pedicle foramen of acrotretids was proposed by Popov (1992), and seemingly corroborated by observations of Ushatinskaya & Korovnikov (2016R), who note that the propareas of the Botsfordia ventral valve sometimes merge to form an elongate teardrop-shaped pedicle foramen.
Clupeafumosus socialis: Following Popov (1992), the larval delthyrium is sealed in adults by outgrowths of the posterolateral margins of the shell.
Eoobolus: See for example fig. 5 in Balthasar 2009T.
Glyptoria: “Delthyrium and notothyrium open, wide” – Cooper 1976.
Longtancunella chengjiangensis: Unclear: a narrow ridge that may correspond to a pseudodeltidium evident in fig 2a and sketched in fig. 2c is not discussed in the text of Zhang et al. 2011T, so the delthyrial region is coded as ambiguous.
Mickwitzia muralensis: A delthyrium is present in young individuals (Balthasar 2004).
Micrina: Opening inferred by Holmer et al. (2008).
Pelagodiscus atlanticus: The listrum (pedicle opening) is interpreted as originating via a similar mechanism to that of acrotretids (Popov 1992), and hence corresponding to a basally sealed delthyrium.
Siphonobolus priscus: Ontogeny presumed to resemble that of acrotretids.
Tonicella: The antemucronal area (Schwabe, 2010) is treated as equivalent to the brachiopod delthyrium.
Yuganotheca elegans: Details of the hinge region are unclear due to the flattened and overprinted nature of fossil preservation.
[157] Posterior surface: Delthyrium: Shape
Character 157: Sclerites: Ventral valve: Posterior surface: Delthyrium: Shape
A parallel-sided delthyrium links Mummpikia with the Obolellidae (Balthasar 2008).
Following Popov (1992), the larval delthyrium of acrotretids and allied taxa is understood to be sealed in adults by outgrowths of the posterolateral margins of the shell. The resultant round or teardrop-shaped foramen corresponds the delthyrium.
Askepasma toddense: Prominently triangular (see Topper et al. 2013T, fig. 2).
Clupeafumosus socialis: Following the model of Popov (1992).
Mickwitzia muralensis: An opening is incorporated at the base of the homeodeltidium when the organism switches from early to late maturity (fig. 10 in Balthasar 2004). This opening is conceivably homologous with the pedicle foramen of acrotretid brachiopods and their ilk. To reflect this possible homology, Mickwitzia is coded as polymorphic (triangular/round).
[158] Posterior surface: Delthyrium: Shape: Aspect of rounded opening
Character 158: Sclerites: Ventral valve: Posterior surface: Delthyrium: Shape: Aspect of rounded opening
Chen et al. (2007) propose that an oval to rhombic foramen characterises the discinids (and Heliomedusa, though the foramen in this taxon has since been reinterpreted by Zhang et al. (2009) as an impression of internal tissue).
Lingulellotreta malongensis: Oval (Williams et al. 2000).
Mickwitzia muralensis: Wider than long: see fig. 10 in Balthasar 2004.
[159] Posterior surface: Delthyrium: Cover
Character 159: Sclerites: Ventral valve: Posterior surface: Delthyrium: Cover
An open delthyrium links Mummpikia with the Obolellidae (Balthasar 2008).
The delthyrial opening can be covered by one or more deltidial plates, or a pseudodeltitium.
Inapplicable in taxa with a round delthiruym (generated by overgrowth of the delthyrial opening by posterolateral parts of the shell, per Popov 1992).
Askepasma toddense: Open (Topper et al. 2013T).
Botsfordia: See pl. 3 fig. 15 in Skovsted & Holmer (2005).
Coolinia pecten: A convex pseudodeltidium completely covers the delthyrium in Coolinia.
Glyptoria: Coded as open by Williams et al. (1998T).
Micromitra: Williams et al. 2000, fig. 83.3.
Nisusia sulcata: “Covered only apically by a small convex pseudodeltitium” – Holmer et al. 2018E.
Character 161: Sclerites: Ventral valve: Posterior surface: Delthyrium: Cover: Identity
This character has the capacity for further resolution (one or more deltidial plates), but this is unlikely to affect the results of the present study.
The pseudodelthyrium is also referred to as a homeodeltidium.
The antemucronal area of Polyplacophora is treated as equivalent to the brachiopod delthyrium, but is not depositionally distinct to the rest of the shell, so is coded with a distinct character state.
Alisina: Stated as “concave pseudodeltidium with median plication” – Williams et al. 2000
Coded as “Pseudodeltidium: Covered by concave plate” by Bassett et al. (2001).
Askepasma toddense: No pseudodeltidium (Williams et al. 2000, p. 153).
Gasconsia: A homeodeltidium is illustrated by Hanken & Harper (1985).
Lingulellotreta malongensis: The subapical flange of the Paterimitra S1 sclerite has been homologised with the ventral homeodeltidium of Micromitra (Larsson et al 2014).
Mickwitzia muralensis: Termed a homoedeltidium by Balthasar (2004).
Micrina: “Ventral valve convex with apsacline interarea bearing delthyrium, covered by a convex pseudodeltidium” – Holmer et al. 2008.
Character 162: Sclerites: Ventral valve: Posterior surface: Delthyrium: Pseudodeltidium: Shape
A ridge-like (i.e. convex) pseudodeltitium unites Salanygolina with Coolinia and other Chileata (Holmer et al. 2009, p. 6).
Alisina: “concave pseudodeltidium with median plication” – Williams et al. 2000
Coded as “Pseudodeltidium: Covered by concave plate” by Bassett et al. (2001).
Antigonambonites planus: Convex (Williams et al. 2000, fig. 508).
Kutorgina chengjiangensis: Difficult to determine based on material presented in Zhang et al (2007R), or indeed for other species in the genus (e.g. Williams et al. 2000; Skovsted & Holmer 2005; Holmer et al. 2018T).
Mickwitzia muralensis: Convex (see Balthasar 2004, fig. 4B).
Micrina: Convex deltoid (Holmer et al. 2008T).
Micromitra: Gently convex (see Williams et al. 2000, fig. 83.3).
Nisusia sulcata: Convex in Nisusia (see Rowell and Caruso, 1985, fig. 8.4).
Paterimitra: Gently convex (see Williams et al. 2000, fig. 83.1).
Salanygolina: “The presence of […] a narrow delthyrium covered by a convex pseudodeltidium, places Salanygolinidae outside the Class Paterinata and strongly suggests affinity to the Cambrian Chileida” – Holmer et al. 2009, p. 9.
Tomteluva perturbata: Convex (Streng et al. 2016).
[163] Posterior surface: Delthyrium: Pseudodeltidium: Hinge furrows
Character 163: Sclerites: Ventral valve: Posterior surface: Delthyrium: Pseudodeltidium: Hinge furrows
After Bassett et al. (2001) character 18, “Hinge furrows on lateral sides of pseudodeltidium”.
Gasconsia: Not evident or illustrated (Hanken & Harper, 1985).
Glyptoria: Coded as absent in Bassett et al. 2001 (table 18.1).
Kutorgina chengjiangensis, Nisusia sulcata: Coded as present in Bassett et al. 2001 (table 18.1).
Salanygolina: The presence of this feature is impossible to determine based on the available material.
[164] Umbonal perforation
Character 164: Sclerites: Ventral valve: Umbonal perforation
Certain taxa, particularly those with a colleplax, exhibit a perforation at the umbo of the ventral valve. This opening is sometimes associated with a pedicle sheath, which emerges from the umbo of the ventral valve without any indication of a relationship with the hinge.
In contrast, the pedicle of acrotretids and similar brachiopods is situated on the larval hinge line, but is later surrounded by the posterolateral regions of the growing shell to become separated from the hinge line, and encapsulated in a position close to (or with resorption of the brephic shell, at) the umbo (see Popov 1992, pp. 407–411 and fig. 3 for discussion). In some cases, an internal pedicle tube attests to this origin – potentially corresponding to the pedicle groove of lingulids. As such, the pedicle foramen of acrotretids and allies is not originally situated at the umbo; it is instead understood to represent a basally sealed delthyrium.
Bactrotheca: The apical termination of the conical valve is not preserved (Valent et al., 2012).
Clupeafumosus socialis: The presumed pedicle foramen reported by Topper et al. (2013R) is at the ventral valve umbo. No evidence of an internal pedicle tube is present, but we follow Popov (1992) in inferring the encapsulation of the pedicle foramen.
Cupitheca holocyclata: Decollation generates open umbo, sealed secondarily with septum.
Dailyatia: The B and C sclerites of Dailyatia bear small umbonal perforations (Skovsted et al 2015), but these are not considered to be homologous with the ventral valve, so this character is coded as inapplicable – though the possibility that the perforations are equivalent is intriguing.
A1 sclerites typically have a pair of perforations, which are conceivably equivalent to the setal tubes of Micrina (Holmer et al. 2011). The A1 sclerite of D. bacata has a structure that is arguably similar to the ‘colleplax’ of Paterimitra. But the homology of any of these structures to the umbonal aperture of brachiopods is difficult to establish.
Eccentrotheca: The sclerites of Eccentrotheca form a ring that surrounds the inferred attachment structure; the attachment structure does not emerge from an aperture within an individual sclerite. Thus no feature in Eccentrotheca is judged to be potentially homologous with the apical perforation in bivalved brachiopods.
Heliomedusa orienta: There is “compelling evidence to demonstrate that the putative pedicle
illustrated by Chen et al. (2007: Figs. 4, 6, 7) in fact is the mold of a three-dimensionally preserved visceral cavity.” – Zhang et al. 2009.
Lingulosacculus: The apical termination of the fossil is unknown.
Mickwitzia muralensis: The umbo itself is imperforate (Balthasar 2004).
Paterimitra: The presumed pedicle foramen is an opening between the S1 and S2 sclerites, neither of which are perforated (Skovsted et al. 2009).
Siphonobolus priscus: Prominent subcircular perforation at umbo associated with an internal pedicle tube (Popov et al. 2009), thus presumed to share an origin with the acrotretid pedicle foramen.
Tomteluva perturbata: Streng et al (2016) observe “an internal tubular structure probably representing the ventral end of the canal within the posterior wall of the pedicle tube”, but do not consider this tomteluvid dube to be homologous with the pedicle tube of acrotretids and their ilk, stating (p. 274) that it appears to be unique within Brachiopoda.
[165] Umbonal perforation: Shape
Character 165: Sclerites: Ventral valve: Umbonal perforation: Shape
The perforation in Cupitheca seems to have a distinct origin, arising through decollation; as such, the shape simply reflects the outline of the shell. This reflects a distinct origin of the perforation and is therefore provided as a separate state.
Acanthotretella spinosa: Too small to observe given quality of preservation (Holmer & Caron 2006).
Alisina: Seemingly circular (Zhang et al. 2011A).
Antigonambonites planus: Based on p.92, fig.4B.
Clupeafumosus socialis: Taller than wide in some cases, but very nearly circular in others; see Topper et al. (2013R).
Coolinia pecten: Bassett and Popov write “a dominant feature of the ventral umbo is a sub-oval perforation about 270 μm long and 250 μm wide”: the width and height of this structure are almost identical, and we score it as (sub) circular.
Heliomedusa orienta: Rhombic to oval – seen as evidence for a discinid affinity (Chen et al. 2007).
Kutorgina chengjiangensis: The exact size and shape of the apical perforation is obscured by the emerging pedicle.
Nisusia sulcata: “close to circular” (Holmer et al. 2018E).
Salanygolina: Essentially circular (Holmer et al. 2009, fig. 4).
[166] Colleplax, cicatrix or pedicle sheath
Character 166: Sclerites: Ventral valve: Colleplax, cicatrix or pedicle sheath
In certain taxa, the umbo of the ventral valve bears a colleplax, cicatrix or pedicle sheath; Bassett et al. (2008) consider these structures as homologous.
Bactrotheca: The apical termination of the conical valve is not preserved (Valent et al., 2012).
Botsfordia: Following Williams et al. 1998T, appendix 2.
Clupeafumosus socialis: Not reported by Topper et al. (2013R).
Craniops: Paracraniops is “externally similar to Craniops, but lacking cicatrix” – indicating that Craniops bears a cicatrix (Williams et al. 2000). Also coded as present in their table 15.
Heliomedusa orienta: A cicatrix was reconstructed by Jin & Wang 1992 (figs 6b, 7), but has not been reported by later authors; possibly, as with the ‘pedicle foramen’ of Chen et al. (2007), this structure represents internal organs rather than a cicatrix proper (Zhang et al. 2009); as such it has been recorded as ambiguous.
Kutorgina chengjiangensis: The umbonal region of kutorginides “clearly lacks a pedicle sheath” (Holmer et al. 2018T).
Lingulellotreta malongensis: The pedicle is identified as such (rather than a pedicle sheath) by the internal pedicle tube.
Longtancunella chengjiangensis: A ring-like structure surrounding the pedicle is interpreted as a colleplax (Zhang et al. 2011T), though the authors make no comparison with the pedicle capsule exhibited by extant terebratulids (see Holmer et al. 2018E).
Micrina: Absent in Micrina (Holmer et al. 2011).
Pedunculotheca diania: The flat apical termination of juvenile individuals possibly functioned as colleplax for attachment, but may simply represent the brephic shell; we treat it as ambiguous to reflect this potential homology.
Siphonobolus priscus: Coded as present in view of the attachment scar, which has been considered homologous with the “adult colleplax and foramen with attachment pad” in Salanygolina (Popov et al. 2009).
Tomteluva perturbata: The internal canal associated with the pedicle is unique to the tomteluvids, and has an uncertain identity (Streng et al. 2016). It could conceivably correspond to an internalized pedicle sheath or an equivalent structure, so this feature is coded as ambiguous here.
Ussunia: Following table 15 in Williams et al. 2000.
Yuganotheca elegans: The median collar or conical tube is conceivably homologous with the pedicle sheath.
[167] Median septum
Character 167: Sclerites: Ventral valve: Median septum
Chen et al. (2007) observe a median septum in what they interpret as the ventral valve of Heliomedusa, and the ventral valve of Discinisca, which they propose points to a close relationship.
Acanthotretella spinosa: Carbonaceous preservation confounds the identification of internal shell structures; it is possible that this feature is present, but not observable in the Burgess Shale material.
Botsfordia: Following Williams et al. 1998T, appendix 2.
Clupeafumosus socialis: A short medial ridge (septum) is present in the ventral valve (Topper et al. 2013R).
Eoobolus: Prominent median septum (fig. 4d, e in Balthasar 2009T).
Gasconsia: Evident in moulds of ventral valve (Hanken & Harper, 1985; Watkins, 2002).
Glyptoria: Neither evident nor reported in Williams et al. (2000).
Haplophrentis carinatus: The carina of H. carinatus is an angular elevation of the ventral valve surface, rather than a septum growing inward on the interior of shell.
Heliomedusa orienta: Reported on ‘ventral’ valve by Chen et al. (2007); we consider the ‘ventral’ valve to be the dorsal valve.
Lingulellotreta malongensis: Medial septum visible in ventral valve in Williams et al. (2000), fig. 34.1c.
Micromitra: Ventral ridge characteristic of Micromitra (Skovsted & Peel 2010).
Mummpikia nuda: “Some specimens also reveal that the vault had a slight median septum, which is now visible as a notch or a groove dividing the right from the left part” – Balthasar 2008.
Novocrania: Valve thin and often unmineralized.
Pelagodiscus atlanticus: Described as present in Discinisca by Chen et al. 2007; assumed present also in Pelagodiscus.
Siphogonuchites multa: Seemingly present in S. multa(Bengtson, 1992, fig. 2), though this is not interpreted as a ventral valve.
Siphonobolus priscus: Present; see Popov et al. 2009, fig. 5J.
Ussunia: Following char. 42 in table 15 in Williams et al. 2000.
4.16 Sclerites: Ornament
[168] Concentric ornament
Character 168: Sclerites: Ornament: Concentric ornament
After character 11 in Williams et al. (1998T). Coded as transformational as it is possible that maintaining a smooth shell without occasional prominent ridges requires greater secretory control.
Acaenoplax hayae: None evident (???).
Askepasma toddense, Micromitra, Glyptoria, Kutorgina chengjiangensis, Salanygolina: Following appendix 2 in Williams et al. (1998T).
Bactrotheca: Both valves with fine growth lines only (Valent et al., 2012).
Botsfordia: Following Williams et al. 1998T, appendix 2.
Pustules are arranged along concentric growth lines (Skovsted & Holmer, 2005), so are not treated as a distinct ornamentation.
Calvapilosa kroegeri: Prominent ridge in certain specimens (Vinther et al., 2017).
Conocardium elongatum: Some concentric ornament evident in some regions of the shell (Rogalla & Amler, 2003).
Halkieria evangelista: Ridges in shell parallel, but are more prominent than, growth lines.
Haplophrentis carinatus: A series of regularly spaced concentric ridges adorn both valves (Moysiuk et al. 2017); these are more pronounced than mere growth lines.
Heliomedusa orienta: The ornament on shell exterior is described as concentric fila (Chen et al., 2007, P.43), and also scored as it in Williams et al. (2000, pp.160–163).
Novocrania: Irregular ridges externally (Williams et al. 2000).
Orthrozanclus: Concentric ridges in addition to growth lines (Conway Morris & Caron, 2007).
Pedunculotheca diania: A series of regularly spaced concentric ridges adorn the ventral valve; comparatively less regular lines ornament the operculum.
Pelagiella: Ornament, if present, is not concentric.
Pelagodiscus atlanticus: Only growth lines evident (Williams et al. 2000).
Terebratulina: Single ridge evident in Williams et al. (2006) fig. 1425.1a interpreted as interruption ot growth rather than inherent feature, so coded as absent (i.e. smooth).
Tonicella: No prominent ornamentat in Tonicella(Connors et al., 2012).
Novocrania: Clear outer faces (Williams et al. 2000, fig. 100.2b).
Orthrozanclus: Preservation inadequate to determine.
[170] Radial ornament
Character 170: Sclerites: Ornament: Radial ornament
Ridges radiating from umbo, i.e. ribs.
Askepasma toddense: “Ornament of irregularly developed, concentric growth lamellae; microornament of irregularly arranged, polygonal pits” – Williams et al. 2000, p153; figs on p.155.
Botsfordia: Following Williams et al. 1998T, Appendix 2.
Calvapilosa kroegeri: Radial structures interpreted as aesthete canals (Vinther et al., 2017).
Eoobolus: Very faint costellae in some specimens but coded absent.
Gasconsia: “Ornament of indistinct low radial ribs” – Williams et al. (2000, p167).
Glyptoria: “Coarsely costate” – Williams et al. (2000, p710).
Haliotis: Radial (apical to apertural) lineations present (Auzoux-Bordenave et al., 2010).
Heliomedusa orienta: See fig. 1715 in Williams et al. (2007).
Orthrozanclus: Not evident (Conway Morris & Caron, 2007).
Siphogonuchites multa: No treated as homologous to those of brachiopods, due to their inferred homology with setae.
Tonicella: Aesthete canals penetrate the main valves of certain chitons, but are not equivalent to the shell-penetrating spines of brachiopods.
4.17 Sclerites: Composition
[172] Mineralogy
Character 172: Sclerites: Composition: Mineralogy
Acaenoplax hayae: Preserved as calcite, but interpreted as aragonitic (???).
Acanthotretella spinosa: Holmer & Caron (2006) note the absence of brittle breakage, interpreted as indicating the absence of a material mineralized component to the shells. The preservation is strikingly different from that of other Burgess Shale brachiopods, ruling out a primarily calcitic or phosphatic composition. The two-dimensional nature of the preservation also differs from that of co-occurring aragonitic taxa (hyoliths; Holmer & Caron 2006 p. 273), indicating that any mineralization was minor at best.
Holmer & Caron (2006, p. 286) suggest that it is more likely that a (minor) mineral component was present than that it was not, though without providing an uncontestable rationale. To be as conservative as possible, we therefore code this taxon as ambiguous.
Calvapilosa kroegeri: Calcareous (Vinther et al., 2017).
Clupeafumosus socialis: Phosphatic – hence the conventional placement within Linguliformea.
Conocardium elongatum: Entirely aragonitic in Apotocardium(Rogalla, Carter, & Pojeta, 2003).
Cotyledion tylodes: The extensive relief and association with pyrite framboids indicates original mineralization, but the identity of the biomineral remains uncertain (Zhang et al., 2013).
Craniops: Shell calcitic.
Cupitheca holocyclata: Reconstructed as aragonitic from microstructural fabrics (Vendrasco et al., 2017).
Eoobolus: “the original shell of Eoobolus contained small calcareous grains that were incorporated into organic-rich layers alongside apatite” (Balthasar 2007).
Gasconsia: Confirmed in Trimerella by Balthasar et al. 2011.
Haliotis: “Essentially made of aragonite” (Auzoux-Bordenave et al., 2010).
Heliomedusa orienta: “Shell originally organophosphatic, but may generally have been poorly mineralized” – Williams et al. 2007 – cf. ibid, p. 2889, “These strong similarities to discinoids in soft-part anatomy imply that the Heliomedusa shell was chitinous or chitinophosphatic, not calcareous.”
Kulindroplax perissokomos: Presumed calcareous.
Lingulellotreta malongensis: Coded as phosphatic by Zhang et al. (2014), but with no explanation.
Cracks within shells of Chengjiang specimens (e.g. Zhang et al. 2007N, fig. 3) demonstrate that the shells were originally mineralized, but not the identity of the original biomineral. This said, phosphatized material from Kazakhstan (Holmer et al. 1997) is attributed to the same species; presuming this phosphate to be original and the material to be conspecific, L. malongensis is coded as having phosphatic shells.
Lingulosacculus: The absence of relief in Lingulosacculus rules out a phosphatic or calcitic composition, but co-occurring (and presumably aragonitic) hyolithids are preserved in the same fashion. Its constitution was thus either organic or aragonitic (Balthasar & Butterfield 2009E).
Longtancunella chengjiangensis: “The original composition of the shell cannot be determined with certainty”, though it was “most probably entirely soft and organic” – Zhang et al. 2011T.
Mickwitzia muralensis: Calcite and silica deemed diagenetic by Balthasar (2004).
Mummpikia nuda: Identified as calcareous by preservational criteria, and description “primary
calcitic shells of M. nuda” (Balthasar 2008).
Novocrania: Ventral valve uncalcified in extant forms or sometimes thin (Williams et al., 2000), but coded as calcitic as calcite-mineralizing pathways are present.
Orthrozanclus: Relief indicates original mineralization, presumably in calcium carbonate as the originally phosphatic biominerals retain their original composition in Burgess Shale palaeoscolecids (???).
Pelagiella: Aragonite (???).
Pojetaia runnegari: Originally comprised spherulitic aragonite prisms (???).
Polysacos vickersianum: By analogy with close relative Protobalanus(Vinther et al., 2012).
Salanygolina: Original mineralogy unknown, but known to be mineralised and anticipated to be phosphatic (Holmer et al. 2009).
Siphogonuchites multa: Interpreted as aragonitic (Bengtson, 1992).
Ussunia: Trimerellids were probably aragonitic (Williams et al., 2000).
Yilingia spiciformis: Presumably non-mineralized, on account on the absence of equivalent features in the shelly fossil record.
[173] Cuticle or organic matrix
Character 173: Sclerites: Composition: Cuticle or organic matrix
Williams et al. (1996) identify glycoprotein-based organic scaffolds as distinct from those comprising glycosaminoglycans (GAGs), chitin and collagen. This character can only be scored for extant taxa.
Haliotis: “The organic matrix [..] is a mixture of proteins, glycoproteins, lipids, chitin and acidic polysaccharides” (Auzoux-Bordenave et al., 2010) – no GAGs or collagen.
Lingula: Coded as GAGs, chitin and collagen in lingulids by Williams et al (1996).
Mytilus: Glycolytic domain containing proteins were observed (=glycoproteins?), whereas GAGs were not (Gao et al., 2015).
Novocrania: Coded as glycoprotein for craniids by Williams et al (1996).
Pelagodiscus atlanticus: Coded as GAGs, chitin and collagen in discinids by Williams et al (1996).
Phoronis: “The presence of sulphated glycosaminoglycans (GAGs) in the chitinous cuticle of Phoronis (Herrmann, 1997, p. 215) would suggest a link with linguliforms, as GAGs are unknown in rhynchonelliform shells (Fig. 1891, 1896)” – Williams et al. 2007, p. 2830.
Siphonobolus priscus: Lenticular chambers in siphonotretid shells interpreted as degraded GAG residue (Williams et al. 2004).
Terebratulina: Coded as glycoprotein for terebratulids by Williams et al (1996).
[174] Incorporation of sedimentary particles
Character 174: Sclerites: Composition: Incorporation of sedimentary particles
Phoronids and Yuganotheca aggulutinate particles into their sclerites.
[175] Microstructure: Number of distinct layers
Character 175: Sclerites: Composition: Microstructure: Number of distinct layers
Hyolith conchs comprise two mineralized layers of fibrous bundles. Bundles are measure 5–15 μm across; their constituent fibres are each 0.1–1.0 μm wide. In the inner layer, the fibres are transverse; in the outer layer, the bundles are inclined towards the umbo, becoming longitudinal on the outermost margin.
Coded as non-additive as there is no clear necessity to add layers sequentially: for example, three layers could arise by the addition of a void within a single pre-existing layer.
Stratiform laminae, shell-penetrating canals and other features above the scale of crystal organization are not considered as contributing to the mineralogical microstructure and are coded separately.
Inapplicable in taxa with a non-mineralized shell.
Bactrotheca: Taxon known only from moulds (Valent et al., 2012).
Botsfordia: “Composed of a thin primary layer and a laminate secondary shell exhibiting baculate shell structure” – Skovsted & Holmer (2005), with reference to Skovsted & Holmer 2003.
Clupeafumosus socialis: General acrotretid structure taken from Zhang et al. (2016).
Conocardium elongatum: Two layers are microstructrually differentiated; the ‘inner’ layer is considered a sub-layer of the ‘middle’ layer (Rogalla et al., 2003).
Cupitheca holocyclata: Inner and outer layers (Vendrasco et al., 2017).
Eoobolus: “Eoobolus shells exhibit the general characteristics of modern linguliform shells, i.e. they were composed of alternating sets of organic and apatite-rich layers that were separated by thin sheets of recalcitrant organic layers.” – Balthasar 2007.
Haliotis: (In juveniles): tablets plus inner and outer prismatic layers (Auzoux-Bordenave et al., 2010).
Halkieria evangelista: Single layer of fibrous aragonite (Porter, 2008).
Leptochiton: (???).
Mickwitzia muralensis: “the shell structure of Mickwitzia […] is closely similar to the columnar shell of linguliform acrotretoid brachiopods as well as to the linguloid Lingulellotreta, in that it has slender columns in the laminar succession” – Williams et al. 2007.
Micrina: Identical to Mickwitzia and more derived linguliforms (Holmer et al 2011).
Mummpikia nuda: Balthasar (2008) considers the single mineralogical layer, which comprises phosphatic rods and laminae, to characterize Obolellata.
Mytilus: Aragonitic nacre, fibrous calcite prisms, and myostracum (Gao et al., 2015).
Namacalathus: Namacalathus exhibits three layers, none of which have any obvious correspondence with those of brachiopods.
Neopilina: “Shell layers consisting of a thin periostracum, a dominant prismatic layer, and a thin internal nacreous layer” (McLean, 1979)
“Spherulitic aragonitic prisms beneath the organic periostracum” (???).
Paramicrocornus: “The shells of both skeletal components show very similar structures and are composed of two layers” – Z.-L. Zhang et al. (2018).
Pelagiella: At least three microstructures are evident, although it is not quite apparent whether these occur in separate layers or separate regions of the shell (???).
Siphonobolus priscus: “Orthodoxly secreted primary and secondary layers” – Williams et al. 2004.
Tonicella: From periostracum inwards, Chiton bears three microstructural layers: fine-grained, nacreous, and regular crossed lamellar.
[176] Microstructure: Format
Character 176: Sclerites: Composition: Microstructure: Format
Hyolith conchs comprise two mineralized layers of fibrous bundles. Bundles measure 5–15 μm across; their constituent fibres are each 0.1–1.0 μm wide. In the inner layer, the fibres are transverse; in the outer layer, the bundles are inclined towards the umbo, becoming longitudinal on the outermost margin.
Stratiform laminae, shell-penetrating canals and other features above the scale of crystal organization are not considered as contributing to the mineralogical microstructure and are coded separately.
The pervasive (not just superficial) polygonal structures in Paterimitra are distinct, and characterize Askepasma, Salanygolina, Eccentrotheca and Paterimitra (Larsson et al. 2014)
Williams et al. (2000) identify cross-bladed laminae as diagnostic of Strophomenata, with the exception of some older groups that contain fibres or laminar laths.
Antigonambonites planus: Tabular laminae, not fibrous as previously thought (Madison, 2017).
Askepasma toddense: Lamination present (Balthasar, Skovsted, Holmer, & Brock, 2009), with imprints of presumed mantle cells (following Williams et al., 1998b, appendix 2).
Botsfordia: “Composed of a thin primary layer and a laminate secondary shell exhibiting baculate shell structure” – Skovsted & Holmer (2005), with reference to Skovsted & Holmer 2003.
Williams et al. (1998b appendix 2) code lamination as present, with no imprints of presumed mantle cells.
Conocardium elongatum: Spherulitic prisms are present in the outer layer of Apotocardium; crossed lamellae or prisms in the inner (Rogalla et al., 2003).
Lingula: Lingulid laminae are thicker than those of tommotiids or paterinids, but construed as homologous (Balthasar et al., 2009).
Mickwitzia muralensis: Alternation of layers (Balthasar, 2004).
Micrina: Micrina exhibits polygonal imprints on the internal surfaces of successive second-order laminae, suggesting the existence of a polygonal organization of these layers (Balthasar et al., 2009).
Mummpikia nuda: Balthasar (2008) considers the single mineralogical layer, which comprises phosphatic rods and laminae, to characterize Obolellata.
Namacalathus: The inner and outer layer are foliated. The columnar inflections lack canals, and as such we do not consider them to bear any obvious homology with the hollow pillars of tommotiids and certain brachiopods, their superficial similarity to strophomenid pseudopunctae notwithstanding.
Neopilina: “Shell layers consisting of a thin periostracum, a dominant prismatic layer, and a thin internal nacreous layer” (McLean, 1979).
Tomteluva perturbata: No original structural details evident (Streng et al., 2016).
4.18 Sclerites: Structure
[177] Stratiform lamellae expressed at surface
Character 177: Sclerites: Structure: Stratiform lamellae expressed at surface
In tommotiids, the shell simply comprises a stack of stratiform lamellae, each corresponding to a circumferential rib at the shell surface. This is particularly apparent in Dailyatia(Skovsted et al., 2015) and Paterimitra(C. M. Larsson et al., 2014).
Salanygolina: Laminae seem to terminate at superficial ridges (Holmer et al., 2009).
Siphonobolus priscus: (Williams et al. 2004).
[178] Stratiform laminae separated
Character 178: Sclerites: Structure: Stratiform laminae separated
Laminae within, for example, Salanygolina are separated by voids that may originally have contained organic material (e.g. Holmer et al., 2009). In contrast, tommotiids and paterinids exhibit stratification without voids, perhaps representing periodic fluctuations in phosphate availability (Balthasar et al., 2009).
Askepasma toddense, Eccentrotheca: Contiguous (Balthasar et al., 2009).
Botsfordia: Skovsted & Holmer 2003.
Clupeafumosus socialis: Acrotretid laminae are separated by column-supported voids.
Salanygolina: Polygonally-filled voids (Holmer et al., 2009).
Siphonobolus priscus: (Williams et al. 2004).
[179] Stratiform laminae with polygonal ornament
Character 179: Sclerites: Structure: Stratiform laminae with polygonal ornament
See character 37 in Williams et al. (1998b).
“A distinct primary layer […] is characterized by a polygonal ornament that is mineralized from the polygon walls inward, while the rest of the shell and/or sclerite is secreted by basal accretion” – Balthasar et al. (2009). Distinguished from epithelial cell moulds in lingulids, which do not form an integral part of the shell structure (Balthasar et al., 2009).
Treated as transformational as ancestral condition is ambiguous.
Askepasma toddense, Eccentrotheca, Paterimitra: Present (Balthasar et al., 2009).
Micromitra, Botsfordia, Eoobolus: Lamination present, with no imprints of presumed mantle cells (following Williams et al., 1998b, appendix 2).
Clupeafumosus socialis: Epithelial cell moulds present on inner shell layer in acrotretids (Z.-L. Zhang, Zhang, & Wang, 2016).
Dailyatia: Polygonal structures on external surface of sclerites only (Skovsted et al., 2015); not reported from other camenellans (Balthasar et al., 2009).
Lingula: Absent in Lingula, though potentially equivalent, if superficial (Balthasar et al., 2009), features adorn Lingulella(Curry & Williams, 1983).
Micrina: Micrina exhibits polygonal imprints on the internal surfaces of successive second-order laminae, suggesting the existence of a polygonal organization of these layers (Balthasar et al., 2009).
Mummpikia nuda: It is conceivable that the rods (Balthasar 2008) correspond to the polygonal ornament observed in other taxa; coded as ambiguous.
Salanygolina: Prominently present (Holmer et al., 2009).
Siphonobolus priscus: (Williams et al. 2004).
[180] Canals
Character 180: Sclerites: Structure: Canals
A caniculate microstructure occurs in lingulids; canals are narrower (< 1 μm) than punctae, may branch, and do not fully penetrate the shell, terminating just within the boundaries of a microstructural layer. See Williams 1997, p303ff, and Balthasar 2008, p273, for discussion.
Tubules described in hyoliths by Kouchinsky (2000) measure around 10 μm in diameter, making them an order of magnitude wider than lingulid canals.
This said, Balthasar (2008) considers the rod-like tubules within the columnar shell microstructure of Mickwitzia cf. occidens (1–3 μm wide, Skovsted & Holmer 2003), acrotretides (1 μm wide, see Holmer 1989, Zhang et al. 2016) and lingulellotretids (100 nm wide, Cusack et al 1999) as equivalent to lingulid canals.
Micrina exhibits both punctae and canals (Harper et al. 2017), challenging Carlson’s contention (in Williams et al. 2007) that the structures are potentially homologous as shell perforations.
Bactrotheca: Taxon known only from moulds (Valent et al., 2012).
Botsfordia: Not evident in section presented by Skovsted & Holmer (2003).
Balthasar (2008) considers these columns as homologous with tubules within the columnar shell microstructure Mummpikia, Mickwitzia and lingulellotretids.
Cupitheca holocyclata: Orthogonal tubules (Vendrasco et al., 2017).
Halkieria evangelista: The chambers in halkieriid sclerites do not correspond in morphology or dimension to the brachiopod-like canals documented by this character.
Longtancunella chengjiangensis: Preservational resolution not sufficient to evaluate.
Mickwitzia muralensis: Coded as present to reflect similarity of columnar microstructure remarked on by, among others, Balthasar (2008); Williams et al. (2007); Skovsted & Holmer (2003).
Micrina: Acrotretid laminae bear characteristic columns (e.g. Zhang et al. 2016); a similar fabric has been reported, and assumed homologous, in Micrina (Butler et al. 2012).
A similar columnar shell microstructure also occurs in the closely related Mickwitzia (Balthasar 2008).
Namacalathus: Canal-like structures have been reported in Namacalathus (Zhuravlev et al. 2015), and interpreted as evidence for a Lophophorate affinity. Though the structures are not necessarily directly equivalent, the hypothesis of homology is followed here.
Paramicrocornus: Columns, replicated in phosphate and present in both layers of the shell, have been interpreted as potential homologues to acrotretid columns (Z.-L. Zhang et al., 2018).
Siphonobolus priscus: The ‘canals’ through the shell have a diameter of c. 20 μm (Williams et al. 2004, text-fig. 2a), falling within the definition of punctae (rather than canals) used herein.
Tonicella: Aesthete canals do not fall within the definition of this character.
[181] Punctae
Character 181: Sclerites: Structure: Punctae
Punctae are 10–20 μm wide canals created by multicellular extensions of the outer epithelium. They penetrate the full depth of the shell.
Balthasar (2008) writes:
“Vertical shell penetrating structures, such as punctae, pseudopunctae, extropunctae and canals, are common in many groups of brachiopods and are distinguished based on their geometry and size (Williams 1997). Punctae are 10–20 μm wide and represent multicellular extensions of the outer epithelium (Owen and Williams 1969). Pseudopunctae and extropunctae are similar in diameter but, instead of canals, are vertical stacks of conical deflections of individual shell layers (Williams and Brunton 1993). None of these three types of vertical shell structure, all of which are confined to calcitic-shelled brachiopods, compares with the much smaller canals (< 1 μm in diameter) of M. nuda. The only type of vertical structure that fits the size and nature of the canals of the Mural obolellids are the canals of linguliform brachiopods, which range in width from 180 to 740 nm and are occupied by proteinaceous strands in extant taxa (Williams et al. 1992; Williams et al. 1994; Williams et al. 1997). In contrast to obolellid canals, however, linguliform canals are not known to penetrate the entire shell but terminate in organic-rich layers (Williams 1997). Based on these considerations it would, therefore, be misleading to call obolellid shells punctate (they are as much”punctate" as acrotretids or other linguliforms); rather their shell structure should be called canaliculate (Williams 1997)."
Bactrotheca: Taxon known only from moulds (Valent et al., 2012).
Craniops: “impunctate”.
Haplophrentis carinatus: The tubules within the centre of the bundles of hyolith shells (Kouchinsky 2000) are c. 10 μm wide, making them an order of magnitude larger than the canals that characterize lingulid valves, and a similar scale to punctae. This said, they have only been reported in a putative allathecid, so the presence of equivalent structures in hyolithids has never been demonstrated.
Heliomedusa orienta: ‘Identical’ to those in Mickwitzia – see Williams et al. 2007.
Mickwitzia muralensis: Coded as present to reflect that the chambers contained setae; following Carlson in Williams et al. 2007, the punctae may or may not be homologous as punctae, but are likely homologous as shell perforations; both these perforations and those of Micrina were associated with setae, even if their equivalence bay be with juvenile vs adult setal structures in modern brachiopods (Balthasar 2004, p. 397).
Mummpikia nuda: “Vertical shell penetrating structures, such as punctae, pseudopunctae, extropunctae and canals, are common in many groups of brachiopods and are distinguished based on their geometry and size (Williams 1997). Punctae are 10–20 μm wide and represent multicellular extensions of the outer epithelium (Owen and Williams 1969). […] None of these three types of vertical shell structure, all of which are confined to calcitic-shelled brachiopods, compares with the much smaller canals (< 1 μm in diameter) of M. nuda. The only type of vertical structure that fits the size and nature of the canals of the Mural obolellids are the canals of linguliform brachiopods, which range in width from 180 to 740 nm and are occupied by proteinaceous strands in extant taxa (Williams et al. 1992, 1994; Williams 1997).” – Balthasar 2008.
Paramicrocornus: Not evident despite excellent preservation; interpreted as absent (Z.-L. Zhang et al., 2018).
Siphonobolus priscus: The ‘canals’ through the shell have a diameter of c. 20 μm (Williams et al. 2004, text-fig. 2a), falling within the definition of punctae used herein.
Terebratulina: Endopunctae are relatively large canals, diameter vary greatly from 5–20 μm.
[182] Pseudopunctae
Character 182: Sclerites: Structure: Pseudopunctae
Pseudopunctae are not punctae, but deflections of shell laminae. They characterise Strophomenata in particular.
Antigonambonites planus, Glyptoria, Nisusia sulcata: Scored absent in data matrix of Benedetto (2009).
Bactrotheca: Taxon known only from moulds (Valent et al., 2012).
Orthis: Scored absent (in Eoorthis) in data matrix of Benedetto (2009).
Paramicrocornus: Absent (Z.-L. Zhang et al., 2018).
[183] External polygonal ornament
Character 183: Sclerites: Structure: External polygonal ornament
Regular polygonal compartments, around 10 μm in diameter, characterise Paterimitra. Walls between compartments have the cross-section of an anvil. An external polygonal structure (possible imprints of epithelial tissue) occurs in Dailyatia, but it is a surface pattern, which is different from the polygonal prisms in the body wall of other paterinid-like groups.
Clupeafumosus socialis: The polygonal ornament reported in acrotretids by Zhang et al. (2016) is on the internal surface of the shell.
Siphogonuchites multa: Coded present by Vinther et al. (2017), who cite Bengtson (1992).
The incorporated sclerites conceivably correspond to aesthete precursors, but this cannot be decisively established: so coded as ambiguous.
[185] Aesthete canals: Orientation
Character 185: Sclerites: Structure: Aesthete canals: Orientation
Tonicella: Consistently uniform (Vendrasco et al., 2008).
[187] Aesthete canals: Megalaesthete bulbs
Character 187: Sclerites: Structure: Aesthete canals: Megalaesthete bulbs
Megalaesthetes are the large aesthete canals from which smaller chambers emerge. Character ‘lin’ in Vendrasco et al. (2008).
[188] Subapical tunnels
Character 188: Sclerites: Structure: Subapical tunnels
Character 23 in Vinther et al. (2017). Distinct from the umbonal perforation observed in some ventral valves on account of their subapical position. Also termed ‘lacunae’.
[189] Articulamentum
Character 189: Sclerites: Structure: Articulamentum
Character 30 in Vinther et al. (2017). The articulamentum is a secondary layer of shell present in polyplacophorans.
Calvapilosa kroegeri: Coded as absent by Vinther et al. (2017).
Glaphurochiton carbonarius, Polysacos vickersianum: Following Vinther et al. (2017).
Following Carlson (1995), character 7. This character is only possible to code in extant taxa. It is not considered independent of Carlson’s character 11, number of gametes released per spawning, as it is possible to produce more small eggs than large eggs – thus this latter character is not reproduced in the present study. The same goes for Carlson’s character 12, gamete dispersal mode; brooders will tend to brood large eggs.
Amathia: “Mature eggs commonly measure about 200 μm in diameter” (Franzén, 1977); the larva is a similar size (Reed & Cloney, 1982).
Capitella: >200 μm in most species (though 50 μm in some) (Eckelbarger & Grassle, 1983).
Dentalium: Egg size can vary from 60–200 μm in scaphopods, but in Dentalium the eggs are large (Dufresne-Dube, Picheral, & Guerrier, 1983).
Flustra: “Mature eggs commonly measure about 200 μm in diameter” – Franzén (1977).
Haliotis: Up to 200 μm long when fully developed (Martin, Romero, & Miller-Walker, 1983).
Novocrania, Lingula, Pelagodiscus atlanticus, Terebratulina: Following coding for class in Carlson (1995) appendix 1, character 7.
Neopilina: “Usually the mature eggs have an oblong cell body 220–320 μm long and 130–190 μm broad.” (Lemche & Wingstrand, 1959).
Phoronis: Phoronis has planktotrophic larvae. indicating a small egg size (Ruppert et al. 2004). Carlson (1995) codes phoronids as polymorphic, as some members of the phylum have eggs of each size.
Serpula: c. 50 μm in Hydroides(Miles, Hadfield, & Wayne, 2007).
Siphonobolus priscus: “the ventral brephic valve [was] 50 μm across, [which] is close to the known lower limit of the brachiopod egg size” – Popov et al. 2009.
Capitella: “Most ultrastructural features of the eggs in the lateral region of the ovary are indistinguishable from those floating freely in the coelom, although the egg envelopes […] undergo additional differentiation following ovulation […] there is no indication that further maturation occurs before spawning” (Eckelbarger & Grassle, 1983).
Haliotis: Compartments of the ovary wall (Martin et al., 1983).
Novocrania, Lingula, Pelagodiscus atlanticus, Terebratulina: Following Hodgson & Reunov (1994).
Mytilus: Mature eggs within the ovary (Humphreys, 1962).
Character 202: Gametes: Spermatozoa: Nucleus: Nuclear filament
A nuclear filament is an anterior extension of the nucleus that terminates at the acrosome, present in lepidopleurid chitons (Buckland-Nicks, 2008, character 6).
Sipunculus: A peaked disc in Phascolion(Rice, 1993).
Terebratulina: Disc-shaped (in Kraussina) (Hodgson & Reunov, 1994).
Wirenia: Conical (in Epimenia; Buckland-Nicks, 2008, character 2).
[206] Acrosome: Differentiated internally
Character 206: Gametes: Spermatozoa: Acrosome: Differentiated internally
Hodgson & Reunov 1994 describe the Discinisca acrosome as having “an electron-lucent centre and an electron-dense outer region”, and state that this trait is characteristic of inarticulate brachiopods. The interstitial granule of certain polyplacophorans represents a separate mode of acrosome differentiation. The subacrosomal granule and subacrosomal basal plate are treated separately, and are not considered to represent internal differentiation.
Flustra, Amathia: No evidence of internal differentiation (in Tubulipora; Franzén, 1984).
Capitella: Electron dense rings the the acrosome vesicle (Eckelbarger & Grassle, 1987).
Chaetoderma: Not differentiated, following character 2 of Buckland-Nicks (2008).
Dentalium: Differentiated membrane only (Dufresne-Dube et al., 1983).
Haliotis: “The large acrosome granule contains two distinct components: (1) an ovoid electron-dense body in the anterior apex of the granule […], and (2) a less dense, homogeneous material at the granule posterior.” (Lewis et al., 1980).
Leptochiton: The acrosome is a cone with subacrosomal granule and subacrosomal plate, but not interstital granule, following character 2 of Buckland-Nicks (2008).
Lingula: Clear differentiation of marginal area (Fukumoto 2003).
Loxosomella: Not evident in Loxosoma(Franzén, 2000).
Mopalia: The acrosome is a cone with subacrosomal granule, interstitial granule, and subacrosomal plate, following character 2 of Buckland-Nicks (2008).
Mytilus: Material lines acrosomal membrane (Niijima, 1965).
Neopilina: Not consistently differentiated in Laevipilina(Healy et al., 1995).
Novocrania: “Along the inner and outer margins there are periodically banded layers, and between them there is a less dense layer” – Afzelius & Ferraguti, 1978.
Pelagodiscus atlanticus: Following Disciniscatenuis, described in Hodgson & Reunov (1994).
Phoronis: Acrosome-like structure; no internal division or surrounding membrane, with possibility that much of the acrosome is secondarily lost (Reunov & Klepal 2004).
Sipunculus: No differentiation within acrosomal vesicle (Rice, 1993).
Terebratulina: Following Hodgson & Reunov (1994).
Tonicella: “One can distinguish two components in the acrosome, an apical and a basal granule” – Buckland‐Nicks et al. (1988).
Wirenia: In Epimenia, the acrosome is a cone with subacrosomal granule, interstitial granule, and subacrosomal plate, following character 2 of Buckland-Nicks (2008).
[207] Acrosome: Subacrosomal basal plate
Character 207: Gametes: Spermatozoa: Acrosome: Subacrosomal basal plate
Lingula, Terebratulina: Following Hodgson & Reunov (1994).
Loxosomella: “The midpiece consists of two long mitochondrial rods connected with each other by a thin mitochondrial lamella” (Franzén, 2000, in Loxosoma); these are essentially a single organelle surrounding a central rod of electron-dense material.
Neopilina: Coded following Laevipilina(Healy et al., 1995).
Serpula: Five mitochondria surround the base of the flagellum in short midpiece, comparable to that of Sipunculus and Dentalium(Gherardi et al., 2011).
Sipunculus: Short ring of five mitochondria around the central centriole (Rice, 1993).
4.22 Embryo
[217] Micromere size
Character 217: Embryo: Micromere size
Following Hejnol (2010). Blastomeres may undergo significant size differentiation, generating macromeres and micromeres of prominently different sizes.
Flustra, Amathia: In Membranipora, “cleavage is slightly unequal resulting in little larger central
blastomeres” (Gruhl, 2010b).
The “molluscan cross” and “annelid cross” cannot be systematically discriminated from one another, so are treated as a single state.
See characters 127 & 128 in Rouse (1999); 1.49 in von Salvini-Plawen & Steiner (1996);
character 34 in Haszprunar (1996); 35 in Haszprunar (2000); 172 in Giribet & Wheeler (2002).
Flustra, Amathia: Concentration of 30–40 serotonergic perikarya (in Fredericella; Gruhl, 2010a).
Capitella: Two in Platynereis (Marlow et al., 2014).
Haliotis: “As early as Day 5 of embryogenesis, whole-mount ICC revealed an unpaired median cell (UMC) and a bilateral pair of cells that are immunoreactive for serotonin in the anterior region of the animal. Each of the three cells sends one anterior projection and one central projection that forms a dense plexus of serotonergic neurites. By Day 7, a second pair of bilateral cells is added slightly medially and posteriorly to the first pair. [… At] the last larval stage […] additional serotonergic neurons (usually two) [are] detected on each side of the five serotonergic cells.” (Marois & Carew, 1997) The cells are not obviously flask shaped.
Lingula: Cluster of “numerous” serotonergic cells (Altenburger & Wanninger, 2010; Hay-Schmidt, 1992); more than, but probably equivalent to, the flask-shaped cells of Terebratalia(Lüter, 2016).
Loxosomella: Six to eight apical cells; eight peripheral cells (Wanninger, Fuchs, & Haszprunar, 2007), indicating a probable equivalence to polyplacophorans (Haszprunar & Wanninger, 2008).
Mytilus: Four to five vase-shaped cells (Voronezhskaya, Nezlin, Odintsova, Plummer, & Croll, 2008).
Novocrania: Four flask-shaped cells (Altenburger & Wanninger, 2010).
Phoronis: Multiple shapes of cells present (Santagata, 2002); resembles the linguliform arrangement (Altenburger & Wanninger, 2010).
Sipunculus: Cluster of around eight cells, though not quite countable (Wanninger, Koop, Bromham, Noonan, & Degnan, 2005).
Terebratulina: Eight in Terebratalia(Lüter, 2016).
Tonicella: Eight in Ischnochiton and Mopalia(Wanninger et al., 2007).
[225] Develops into adult brain
Character 225: Larva: Apical organ: Develops into adult brain
Mytilus, Haliotis: Following closest relative in Glenner et al. (2004).
Lingula: “both the larval apical ganglion and the ventral ganglion must be retained as
the adult nervous system” (Hay-Schmidt, 1992), but not necessarily as the brain.
[226] Brain persists into adulthood
Character 226: Larva: Brain persists into adulthood
Foot or neurotroch present in larval stage, whether or not it is also present in mature individuals. Following Wingstrand (1985).
Capitella: The neurotroch (Meyer et al., 2010) is a cilliated ventral ‘foot’.
Loxosomella: A foot is present in the creeping-type larva of Loxosomellamurmanica, though absent in L. atkinsae and the many other entoprocts that have swimming-type larvae (Fuchs & Wanninger, 2008).
Sipunculus, Serpula: Wingstrand (1985) considers the annelid neurotroch to be potentially homologous with the molluscan and entoproct foot.
Wirenia: Ciliated foot present in larvae of Epimenia(Okusu, 2002).
[230] Pedal gland
Character 230: Larva: Foot: Pedal gland
A pedal gland is considered evidence for homology between the molluscan and entoproct foot (Haszprunar & Wanninger, 2008).
Amathia: Ciliated clef corresponds to position of foot (Reed & Cloney, 1982), but dedicated foot not present.
Mopalia, Tonicella, Leptochiton: “Absent in adult Polyplacophora but present in early ontogenetic stages” (Wingstrand, 1985).
Wirenia: Pedal pit present in Epimenia(Okusu, 2002).
[231] Pedal gland: Retained to adulthood
Character 231: Larva: Foot: Pedal gland: Retained to adulthood
Characters 1.13, 1.40 & 2.08 in A. H. Scheltema (1993); 114 in Giribet & Wheeler (2002); 1.53 in von Salvini-Plawen & Steiner (1996); 9 in Haszprunar (1996).
Chaetoderma: “Caudofoveata certainly lack […] the pedal gland” (Wingstrand, 1985).
Mopalia, Tonicella, Leptochiton: “Absent in adult Polyplacophora but present in early ontogenetic stages” (Wingstrand, 1985).
Amathia: No evidence of pairing (Reed & Cloney, 1982).
Capitella, Mopalia, Tonicella, Leptochiton, Dentalium, Mytilus, Haliotis: Following figure 13 in A. H. Scheltema (1993).
Flustra: Hypostegal coelom separated from principal (perigastric) body cavity in cheilostomata – but this is not clearly equivalent to the paired coelom intended by this character. The coelom of Fredericella is not paired (Gruhl, 2010a).
[233] Paried: Includes pericardium
Character 233: Larva: Coelom: Paried: Includes pericardium
Flustra: Metamorphose almost immediately after release from gonozooid (Zimmer & Woollacott, 2013); most bryozoans are lecithotrophic (Reed & Cloney, 1982).
Haliotis: (???).
4.24 Larva: Cilia
[235] Metatroch
Character 235: Larva: Cilia: Metatroch
See characters 129 and 131 in Rouse (1999); 40 in Haszprunar (1996).
A prototroch is the defining character of a trochophore larva; a metatroch is a secondary ciliary ring (Rouse, 1999).
The metatroch is present in a subset of annelids; in Polygordius, it derives from the 3c and 3d micromeres, whereas in molluscs the secondary ciliary band derives frmo 2a, 2b and 2c (Meyer et al., 2010). As such, the structures may not be homologous between molluscs and annelids.
Character 238: Larva: Cilia: Ciliary bands: Downstream
Downstream-collecting ciliary bands of compound cilia on multiciliated cells. Character 31 in Glenner et al. (2004).
Capitella: In Chaetopterus (Glenner et al., 2004).
Haliotis: In Littorina (Gastropoda) (Glenner et al., 2004).
Mytilus: In Crassostrea (Bivalvia) (Glenner et al., 2004).
Serpula: “Groups such as Sabellariidae […] have evolved downstream-feeding without the aid of a metatroch” – (Rouse, 2000)In Chaetopterus (Glenner et al., 2004).
Sipunculus: “Taxa such as Sipuncula […] have a metatroch and do not have downstream larval-feeding” – Rouse (2000).
Terebratulina: Following closest relative in Glenner et al. (2004).
[239] Ciliary bands: Upstream
Character 239: Larva: Cilia: Ciliary bands: Upstream
Upstream-collecting ciliary bands with single cilia on monociliated cells. Character 32 in Glenner et al. (2004).
Serpula, Capitella: In Chaetopterus (Glenner et al., 2004).
Haliotis: In Littorina (Gastropoda) (Glenner et al., 2004).
Mytilus: In Crassostrea (Bivalvia) (Glenner et al., 2004).
Terebratulina: Following closest relative in Glenner et al. (2004).
[240] Adoral ciliary band
Character 240: Larva: Cilia: Adoral ciliary band
Characters 1.50, 2.66 and 4.68 in von Salvini-Plawen & Steiner (1996); 2 in Vinther et al. (2008). See also characters 39 in Haszprunar (1996) and 153 in Giribet & Wheeler (2002).
Serpula: Following Enchytraeus(Reger, 1967), Magelona(Bartolomaeus, 1995) and Harmothoe(Holborow et al., 1969).
[248] Ciliary necklace with connecting strands
Character 248: Ciliary ultrastructure: Ciliary necklace with connecting strands
After Lundin et al. (2009).
The ciliary necklace is defined by Gilula & Satir (1972) as “Well-defined rows or strands of membrane particles that encircle the ciliary shaft”. It occurs immediately below the basal plate, and comprises three beaded circles of on the circumference of the cilia membrane.
Character 249: Ciliary ultrastructure: Monociliate epidermal cells
Character 4 in Parry & Caron (2019). Coded as present if compound cilia comprise multiple monociliate cells, even if monociliate cells do not occur individually.
Serpula, Capitella, Mopalia, Tonicella, Leptochiton, Haliotis: Following coding for closest relative in Parry & Caron (2019).
Novocrania, Lingula, Odontogriphus omalus, Wiwaxia corrugata, Halkieria evangelista: Following coding in Parry & Caron (2019).
[250] Presence
Character 250: Ciliary ultrastructure: Compound cilia: Presence
After Lundin et al. (2009). Compound cilia are motile structures composed of 10–100 regular cilia used in locomotion or feeding.
Character 251: Ciliary ultrastructure: Compound cilia: Origin
Character 14 in Glenner et al. (2004). Compound cilia can be produced by the aggregation of cilia from multiple monociliate cells, or from a single cell bearing multiple cilia (Nielsen, 1987).
Capitella, Mytilus, Haliotis: Following closest relative in Glenner et al. (2004).
Terebratulina: “The coelothelial cells of the metacoel are monociliated”; “even some epithelial muscle cells are monociliated” – Lüter (1995).
[252] Glycocalyx ultrastructure
Character 252: Ciliary ultrastructure: Glycocalyx ultrastructure
Character 261: Nephridia: Serve as excretory organs
See character 4.46 in von Salvini-Plawen & Steiner (1996).
Novocrania, Lingula, Pelagodiscus atlanticus, Terebratulina: “The excretory function of the metanephridia in Brachiopoda must be questioned” – Lüter (1995).
Novocrania, Lingula, Sipunculus, Serpula, Capitella, Mopalia, Tonicella, Leptochiton, Haliotis: Following closest relative in Parry & Caron (2019).
[263] Protonephridia
Character 263: Nephridia: Protonephridia
Also termed cyrtocytes. Character 21 in Grobe (2007); 1.47 in von Salvini-Plawen & Steiner (1996); 138 in Rouse (1999); 20 in Haszprunar (1996); 90 in Glenner et al. (2004).
[264] Metanephridia
Character 264: Nephridia: Metanephridia
See characters 35 in Rouse (1999); 28 in Haszprunar (2000); 93 in Glenner et al. (2004); 1.47 in von Salvini-Plawen & Steiner (1996); 21 in Grobe (2007); 138 in Rouse (1999); 20 in Haszprunar (1996).
Amathia: Following closest relative in Glenner et al. (2004).
Lingula, Pelagodiscus atlanticus, Terebratulina: The brachiopod pedicle has a chitinous cuticle (MacKay & Hewitt, 1978; Williams et al., 1997), but the tentacles are associated with collagen (Williams et al., 1997); marked as polymorphic.
Loxosomella: Absent (Haszprunar & Wanninger, 2008). Chitin is occasionally present in certain species, perhaps in regions where rigidity is necessary (Borisanova, Yushin, Malakhov, & Temereva, 2015).
Novocrania: No (chitinous) pedicle, so only collagenous cuticle present (Williams et al., 1997).
Phoronis: Collagen fibres in tentacle cuticle (Bartolomaeus, 2001); chitin only present in tubes (Jeuniaux, 1971).
Character 19 in Haszprunar (1996); see also character 13 in Haszprunar (2000).
Flustra, Amathia: In Bryozoa, myofibrils are “all striated” (Pardos et al., 1991).
Novocrania, Lingula, Pelagodiscus atlanticus, Terebratulina: In brachiopods, myofibrils “are striated on the frontal face and smooth on the abfrontal face” (Pardos et al., 1991).
Phoronis: “In P. australis […] all the myofibrils belong to the smooth type” – Pardos et al. (1991).
Mopalia, Tonicella, Leptochiton: Parry & Caron (2019) code chitons as lacking serial repetition in the nervous system, despite the orthogonal arrangement of nervous tissue.
[277] Glial system
Character 277: Nervous system: Glial system
Character 16 in Haszprunar (1996). The Gliointerstitial system interconnects the nervous and muscle systems.
Phoronis: Glial cells are “abundant” (Temereva, 2016).
[278] Dorso-terminal sense organ
Character 278: Nervous system: Dorso-terminal sense organ
Corresponds to the molluscan osphradium; see (???), character 30; Ponder & Lindberg (1997), character 101; Giribet & Wheeler (2002) character 143; Haszprunar (2000) character 56; (???) character 49; (???) character 101.
[279] Statocysts
Character 279: Nervous system: Statocysts
Character 1.33 in (???); 44 in (???); 99 in Ponder & Lindberg (1997); 55 in Haszprunar (2000).
[280] Nuchal organs
Character 280: Nervous system: Nuchal organs
Character 147 in L. A. Parry et al. (2016), 158 in Parry & Caron (2019).
Nuchal organs are chemosensory organs present in almost all polychaetes, and absent in clitellates. They occur as a dorsal pair of ciliated areas on the posterior prostomium (???). (???) points to a number of differences between the nuchal organs of sipunculans and polychaetes, whilst acknowledging the existence of some similarities; (???) acknowledge that the case is not closed. We agree that homology between the nuchal organs of sipunculans and annelids is uncertain, but code the structures in a single transformation series to allow the analysis to test the hypothesis of homology.
[281] Buccal nerve ring
Character 281: Nervous system: Buccal nerve ring
Character 7b in Haszprunar & Wanninger (2008), following Wanninger et al. (2007). Also termed an oral or circumoral nerve ring.
Loxosomella: A potential synapomorphy uniting Mollusca and Kamptozoa (???; Wanninger et al., 2007).
[282] Anterior nerve loop
Character 282: Nervous system: Anterior nerve loop
Character 7c in Haszprunar & Wanninger (2008), following Wanninger et al. (2007). An anterior, pre-oral nerve loop is present in molluscs, Loxosomella and certain annelids (Wanninger et al., 2007).
Character 288: Nervous system: Cerebral ganglia: Transverse commissures
Character 205 in Parry & Caron (2019), who write “a brain with four transverse commissures is present in numerous families of polychaetes and two commissures are present in Sipuncula”.
Capitella: The brain of Notomastus (Capitellidae) comprises two brain lobes joined by a commissure (???).
Mopalia, Tonicella, Leptochiton, Haliotis: Following closest relative in Parry & Caron (2019).
[289] Serially repeated ganglia
Character 289: Nervous system: Serially repeated ganglia
Novocrania, Lingula, Sipunculus, Canadia spinosa, Serpula, Capitella, Mopalia, Tonicella, Leptochiton, Haliotis: Coded following Parry & Caron (2019), who follow (???).
4.31 MicroRNA
[296] Brachiopod candidate 1
Character 296: MicroRNA: Brachiopod candidate 1
BC1 in 35.
Novocrania, Lingula, Phoronis, Mytilus: 35.
[297] mir-36
Character 297: MicroRNA: mir-36
Phoronis, Capitella, Chaetoderma, Haliotis: 34.
Sipunculus: Following Phascolion(???).
[298] mir-76
Character 298: MicroRNA: mir-76
Phoronis, Capitella, Chaetoderma, Haliotis: 34.
Sipunculus: Following Phascolion(???).
[299] mir-124
Character 299: MicroRNA: mir-124
Phoronis, Capitella, Chaetoderma, Haliotis: 34.
Sipunculus: Following Phascolion(???).
[300] mir-190
Character 300: MicroRNA: mir-190
Phoronis, Capitella, Chaetoderma, Haliotis: 34.
Sipunculus: Following Phascolion(???).
[301] mir-219
Character 301: MicroRNA: mir-219
Phoronis, Capitella, Chaetoderma, Haliotis: 34.
Sipunculus: Following Phascolion(???).
[302] mir-242
Character 302: MicroRNA: mir-242
Phoronis, Capitella, Chaetoderma, Haliotis: 34.
Sipunculus: Following Phascolion(???).
[303] mir-278
Character 303: MicroRNA: mir-278
Phoronis, Capitella, Chaetoderma, Haliotis: 34.
Sipunculus: Following Phascolion(???).
[304] mir-1984
Character 304: MicroRNA: mir-1984
Phoronis, Capitella, Chaetoderma, Haliotis: 34.
Sipunculus: Following Phascolion(???).
[305] mir-1985
Character 305: MicroRNA: mir-1985
Phoronis, Capitella, Chaetoderma, Haliotis: 34.
Sipunculus: Following Phascolion(???).
[306] mir-1986
Character 306: MicroRNA: mir-1986
Phoronis, Capitella, Chaetoderma, Haliotis: 34.
Sipunculus: Following Phascolion(???).
[307] mir-1987
Character 307: MicroRNA: mir-1987
Phoronis, Capitella, Chaetoderma, Haliotis: 34.
Sipunculus: Following Phascolion(???).
[308] mir-1988
Character 308: MicroRNA: mir-1988
Phoronis, Capitella, Chaetoderma, Haliotis: 34.
Sipunculus: Following Phascolion(???).
[309] mir-1989
Character 309: MicroRNA: mir-1989
Phoronis, Capitella, Chaetoderma, Haliotis: 34.
Sipunculus: Following Phascolion(???).
[310] mir-1990
Character 310: MicroRNA: mir-1990
Phoronis, Capitella, Chaetoderma, Haliotis: 34.
Sipunculus: Following Phascolion(???).
[311] mir-1991
Character 311: MicroRNA: mir-1991
Phoronis, Capitella, Chaetoderma, Haliotis: 34.
Sipunculus: Following Phascolion(???).
[312] mir-1994
Character 312: MicroRNA: mir-1994
Phoronis, Capitella, Chaetoderma, Haliotis: 34.
Sipunculus: Following Phascolion(???).
[313] mir-1995
Character 313: MicroRNA: mir-1995
Phoronis, Capitella, Chaetoderma, Haliotis: 34.
Sipunculus: Following Phascolion(???).
[314] mir-1996
Character 314: MicroRNA: mir-1996
Phoronis, Capitella, Chaetoderma, Haliotis: 34.
Sipunculus: Following Phascolion(???).
[315] mir-1997
Character 315: MicroRNA: mir-1997
Phoronis, Capitella, Chaetoderma, Haliotis: 34.
Sipunculus: Following Phascolion(???).
[316] mir-1998
Character 316: MicroRNA: mir-1998
Phoronis, Capitella, Chaetoderma, Haliotis: 34.
Sipunculus: Following Phascolion(???).
[317] mir-1999
Character 317: MicroRNA: mir-1999
Phoronis, Capitella, Chaetoderma, Haliotis: 34.
Sipunculus: Following Phascolion(???).
[318] mir-2000
Character 318: MicroRNA: mir-2000
Phoronis, Capitella, Chaetoderma, Haliotis: 34.
Sipunculus: Following Phascolion(???).
[319] mir-2001
Character 319: MicroRNA: mir-2001
Phoronis, Capitella, Chaetoderma, Haliotis: 34.
Sipunculus: Following Phascolion(???).
[320] mir-2685
Character 320: MicroRNA: mir-2685
Phoronis, Capitella, Chaetoderma, Haliotis: 34.
Sipunculus: Following Phascolion(???).
[321] mir-2686
Character 321: MicroRNA: mir-2686
Phoronis, Capitella, Chaetoderma, Haliotis: 34.
Sipunculus: Following Phascolion(???).
[322] mir-2687
Character 322: MicroRNA: mir-2687
Phoronis, Capitella, Chaetoderma, Haliotis: 34.
Sipunculus: Following Phascolion(???).
[323] mir-2688
Character 323: MicroRNA: mir-2688
Phoronis, Capitella, Chaetoderma, Haliotis: 34.
Sipunculus: Following Phascolion(???).
[324] mir-2689
Character 324: MicroRNA: mir-2689
Phoronis, Capitella, Chaetoderma, Haliotis: 34.
Sipunculus: Following Phascolion(???).
[325] mir-2690
Character 325: MicroRNA: mir-2690
Phoronis, Capitella, Chaetoderma, Haliotis: 34.
Sipunculus: Following Phascolion(???).
[326] mir-2691
Character 326: MicroRNA: mir-2691
Phoronis, Capitella, Chaetoderma, Haliotis: 34.
Sipunculus: Following Phascolion(???).
[327] mir-2693
Character 327: MicroRNA: mir-2693
Phoronis, Capitella, Chaetoderma, Haliotis: 34.
Sipunculus: Following Phascolion(???).
[328] mir-2693
Character 328: MicroRNA: mir-2693
Phoronis, Capitella, Chaetoderma, Haliotis: 34.
Sipunculus: Following Phascolion(???).
[329] mir-2722
Character 329: MicroRNA: mir-2722
Phoronis, Capitella, Chaetoderma, Haliotis: 34.
Sipunculus: Following Phascolion(???).
[330] mir-5045
Character 330: MicroRNA: mir-5045
Novocrania, Lingula, Phoronis, Mytilus: 35.
Tree number:
[Show details]
References
Adrianov, A. V., Maiorova, A. S., & Malakhov, V. V. (2011). Embryonic and larval development of the peanut worm Phascolosoma agassizii (Keferstein 1867) from the Sea of Japan (Sipuncula: Phascolosomatidea). Invertebrate Reproduction and Development, 55(1), 22–29. doi: 10.1080/07924259.2010.548638
Adrianov, A. V., Malakhov, V. V., & Maiorova, A. S. (2006). Development of the tentacular apparatus in sipunculans (Sipuncula): I. Thysanocardia nigra (Ikeda, 1904) and Themiste pyroides (Chamberlin, 1920). Journal of Morphology, 267(5), 569–583. doi: 10.1002/jmor.10423
Altenburger, A., & Wanninger, A. (2010). Neuromuscular development in Novocrania anomala: evidence for the presence of serotonin and a spiralian-like apical organ in lecithotrophic brachiopod larvae. Evolution and Development, 12(1), 16–24. doi: 10.1111/j.1525-142X.2009.00387.x
Altenburger, A., Wanninger, A., & Holmer, L. E. (2013). Metamorphosis in Craniiformea revisited: Novocrania anomala shows delayed development of the ventral valve. Zoomorphology, 132(4), 379–387. doi: 10.1007/s00435-013-0194-3
Auzoux-Bordenave, S., Badou, A., Gaume, B., Berland, S., Helléouet, M.-N., Milet, C., & Huchette, S. (2010). Ultrastructure, chemistry and mineralogy of the growing shell of the European abalone Haliotis tuberculata. Journal of Structural Biology, 171(3), 277–290. doi: 10.1016/j.jsb.2010.05.012
Balthasar, U. (2004). Shell structure, ontogeny, and affinities of the Lower Cambrian bivalved problematic fossil Mickwitzia muralensis Walcott, 1913. Lethaia, 37(4), 381–400. doi: 10.1080/00241160410002090
Balthasar, U. (2007). An early Cambrian organophosphatic brachiopod with calcitic granules. Palaeontology, 50(6), 1319–1325. doi: 10.1111/j.1475-4983.2007.00729.x
Balthasar, U. (2008). Mummpikia gen. nov. and the origin of calcitic-shelled brachiopods. Palaeontology, 51(2), 263–279. doi: 10.1111/j.1475-4983.2008.00754.x
Balthasar, U. (2009). The brachiopod Eoobolus from the early Cambrian Mural Formation (Canadian Rocky Mountains). Paläontologische Zeitschrift, 83(3), 407–417. doi: 10.1007/s12542-009-0026-4
Balthasar, U., & Butterfield, N. J. (2009). Early Cambrian soft-shelled brachiopods as possible stem-group phoronids. Acta Palaeontologica Polonica, 54(2), 307–314. doi: 10.4202/app.2008.0042
Balthasar, U., Skovsted, C. B., Holmer, L. E., & Brock, G. A. (2009). Homologous skeletal secretion in tommotiids and brachiopods. Geology, 37, 1143–1146. doi: 10.1130/g30323a.1
Barlow, L. A., & Truman, J. W. (1992). Patterns of serotonin and SCP immunoreactivity during metamorphosis of the nervous system of the red abalone, Haliotis rufescens. Journal of Neurobiology, 23(7), 829–844. doi: 10.1002/neu.480230705
Bartolomaeus, T. (1995). Secondary monociliarity in the Annelida: monociliated epidermal cells in larvae of Magelona mirabilis (Magelonida). Microfauna Marina, 10, 327–332.
Bartolomaeus, T. (2001). Ultrastructure and formation of the body cavity lining in Phoronis muelleri (Phoronida, Lophophorata). Zoomorphology, 120(3), 135–148. doi: 10.1007/s004350000030
Bartolomaeus, T., & Quast, B. (2005). Structure and development of nephridia in Annelida and related taxa. Hydrobiologia, 535, 139–165. doi: 10.1007/s10750-004-1840-z
Baxter, J. M., Jones, A. M., & Sturrock, M. G. (1987). The infrastructure of aesthetes in Tonicella marmorea (Polyplacophora; Ischnochitonina) and a new functional hypothesis. Journal of Zoology, 211(4), 589–604. doi: 10.1111/j.1469-7998.1987.tb04473.x
Bengtson, S. (1992). The cap-shaped Cambrian fossil Maikhanella and the relationship between coeloscleritophorans and molluscs. Lethaia, 25(4), 401–420.
Bereiter-Hahn, J., Matoltsy, A. G., & Slyvia Richards, K. (1984). Biology of the Integument (p. 858). Springer.
Biggelaar, J. A. M. van den. (1993). Cleavage pattern in embryos of Haliotis tuberculata (Archaeogastropoda) and gastropod phylogeny. Journal of Morphology, 216(2), 121–139. doi: 10.1002/jmor.1052160203
Borisanova, A. O., Yushin, V. V., Malakhov, V. V., & Temereva, E. N. (2015). The fine structure of the cuticle of kamptozoans is similar to that of annelids. Zoomorphology, 134(2), 165–181. doi: 10.1007/s00435-015-0261-z
Brazeau, M. D., Guillerme, T., & Smith, M. R. (2018). An algorithm for morphological phylogenetic analysis with inapplicable data. Systematic Biology. doi: 10.1101/209775
Buckland-Nicks, J. A. (2008). Fertilization biology and the evolution of chitons. American Malacological Bulletin, 25(1), 97–111.
Buckland‐Nicks, J., Koss, R., & Chia, F. ‐. (1988). Fertilization in a chiton: Acrosome‐mediated sperm‐egg fusion. Gamete Research, 21(3), 199–212. doi: 10.1002/mrd.1120210302
Butterfield, N. J. (1990). A reassessment of the enigmatic Burgess Shale fossil Wiwaxia corrugata (Matthew) and its relationship to the polychaete Canadia spinosa Walcott. Paleobiology, 16(3), 287–303. doi: 10.2307/2400789
Byrum, C. A., & Ruppert, E. E. (1994). The ultrastructure and functional morphology of a captaculum in Graptacme calamus (Mollusca, Scaphopoda). Acta Zoologica, 75(1), 37–46. doi: 10.1111/j.1463-6395.1994.tb00960.x
Chen, Z., Zhou, C., Yuan, X., & Xiao, S. (2019). Death march of a segmented and trilobate bilaterian elucidates early animal evolution. Nature. doi: 10.1038/s41586-019-1522-7
Connors, M. J., Ehrlich, H., Hog, M., Godeffroy, C., Araya, S., Kallai, I., … Ortiz, C. (2012). Three-dimensional structure of the shell plate assembly of the chiton Tonicella marmorea and its biomechanical consequences. Journal of Structural Biology, 177(2), 314–328. doi: 10.1016/j.jsb.2011.12.019
Conway Morris, S. (2006). Darwin’s dilemma: The realities of the Cambrian ’explosion’. Philosophical Transactions of the Royal Society of London B: Biological Sciences, 361(1470), 1069–1083. doi: 10.1098/rstb.2006.1846
Conway Morris, S., & Caron, J.-B. (2007). Halwaxiids and the early evolution of the lophotrochozoans. Science, 315(5816), 1255–1258. doi: 10.1126/science.1137187
Conway Morris, S., & Chapman, A. J. (1996). Lower Cambrian coeloscleritophorans (Ninella, Siphogonuchites) from Xinjiang and Shaanxi, China. Geological Magazine, 133(01), 33. doi: 10.1017/S0016756800007238
Curry, G. B., & Williams, A. (1983). Epithelial moulds on the shells of the early Palaeozoic brachiopod Lingulella. Lethaia, 16(2), 111–118. doi: 10.1111/j.1502-3931.1983.tb01706.x
De Viçose, G. C., Viera, M. P., Bilbao, A., & Izquierdo, M. S. (2007). Embryonic and larval development of Haliotis tuberculata coccinea Reeve: An indexed micro-photographic sequence. Journal of Shellfish Research, 26(3), 847–854. doi: 10.2983/0730-8000(2007)26[847:EALDOH]2.0.CO;2
Dewing, K. (2004). Shell structure and its bearing on the phylogeny of Late Ordovician-Early Silurian Strophomenoid Brachiopods from Anticosti Island, Quebec. Journal of Paleontology, 78(2), 275–286. doi: 10.1666/0022-3360(2004)078<0275:SSAIBO>2.0.CO;2
Dufresne-Dube, L., Picheral, B., & Guerrier, P. (1983). An ultrastructural analysis of Dentalium vulgare (Mollusca, Scaphopoda) gametes with special reference to early events at fertilization. Journal of Ultrasructure Research, 83(3), 242–257. doi: 10.1016/S0022-5320(83)90132-6
Dzik, J. (1980). Ontogeny of Bactrotheca and related hyoliths. Geologiska Föreningen i Stockholm Förhandlingar, 102(3), 223–233. doi: 10.1080/11035898009455162
Eckelbarger, K. J., & Grassle, J. P. (1983). Ultrastructural differences in the eggs and ovarian follicle cells of Capitella (Polychaeta) sibling species. The Biological Bulletin, 165(2), 379–393. doi: 10.2307/1541203
Eckelbarger, K. J., & Grassle, J. P. (1987). Spermatogenesis, sperm storage and comparative sperm morphology in nine species of Capitella, Capitomastus and Capitellides (Polychaeta: Capitellidae). Marine Biology, 95(3), 415–429. doi: 10.1007/BF00409572
Ehrlich, H. (2010). Biological materials of marine origin: Invertebrates. Springer.
Fischer, F. P., Maile, W., & Renner, M. (1980). Die Mantelpapillen und Stacheln von Acanthochiton fascicularis L. (Mollusca, Polyplacophora). Zoomorphologie, 94(2), 121–131. doi: 10.1007/BF01081929
Franzén, Å. (1977). Gametogenesis of bryozoans. In R. M. Woollacott & R. L. Zimmer (Eds.), Biology of bryozoans (pp. 1–22). Elsevier.
Franzén, Å. (1981). Comparative ultrastructural studies of spermatids and spermatozoa in Bryozoa and Entoprocta. In G. P. Larwood & C. Nielsen (Eds.), Recent and fossil bryozoans (pp. 83–92). Olsen & Olsen.
Franzén, Å. (1984). Ultrastructure of spermatids and spermatozoa in the cyclostomatous bryozoan Tubulipora (Bryozoa, Cyclostomata). Zoomorphology, 104(3), 140–146. doi: 10.1007/BF00312132
Franzén, Å. (2000). Spermiogenesis, sperm ultrastructure and sperm transport in Loxosoma pectinaricola (Entoprocta). Invertebrate Reproduction and Development, 37(2), 129–136. doi: 10.1080/07924259.2000.9652411
Fuchs, J., & Wanninger, A. (2008). Reconstruction of the neuromuscular system of the swimming-type larva of Loxosomella atkinsae (Entoprocta) as inferred by fluorescence labelling and confocal microscopy. Organisms Diversity and Evolution, 8(4), 325–335. doi: 10.1016/j.ode.2008.05.002
Fuchs, J., Bright, M., Funch, P., & Wanninger, A. (2006). Immunocytochemistry of the neuromuscular systems of Loxosomella vivipara and L. parguerensis (Entoprocta: Loxosomatidae). Journal of Morphology, 267(7), 866–883. doi: 10.1002/jmor.10446
Gherardi, M., Lepore, E., Sciscioli, M., Mercurio, M., Licciano, M., & Giangrande, A. (2011). A study on spermatogenesis of three Mediterranean serpulid species. Italian Journal of Zoology, 78(2), 174–181. doi: 10.1080/11250003.2010.529468
Gilula, N. B., & Satir, P. (1972). The ciliary necklace. The Journal of Cell Biology, 53(2), 494–509. doi: 10.1083/jcb.53.2.494
Giribet, G., & Wheeler, W. C. (2002). On bivalve phylogeny: a high-level analysis of the Bivalvia (Mollusca) based on combined morphology and DNA sequence data. Invertebrate Biology, 121(4), 271–324. doi: 10.1111/j.1744-7410.2002.tb00132.x
Glenner, H., Hansen, A. J., Sørensen, M. V., Ronquist, F., Huelsenbeck, J. P., & Willerslev, E. (2004). Bayesian inference of the metazoan phylogeny; a combined molecular and morphological approach. Current Biology, 14(18), 1644–1649. doi: 10.1016/j.cub.2004.09.027
Goffinet, G., Voss-Foucart, M.-F., & Barzin, S. (1978). Ultrastructure of the cuticle of the sipunculans Golfingia vulgaris and Sipunculus nudus. Transactions of the American Microscopical Society, 97(4), 512–523. doi: 10.2307/3226167
Goodrich, E. S. (1945). The study of nephridia and genital ducts since 1895. The Quarterly Journal of Microscopical Science, 86(344), 113–392.
Gordon, D. P. (1975). The resemblance of bryozoan gizzard teeth to “annelid-like” setae. Acta Zoologica, 56(4), 283–289. doi: 10.1111/j.1463-6395.1975.tb00105.x
Grobe, P. (2007). Larval development, the origin of the coelom and the phylogenetic relationships of the Phoronida (PhD thesis; p. 91). Free University, Berlin.
Gruhl, A. (2008). Muscular systems in gymnolaemate bryozoan larvae (Bryozoa: Gymnolaemata). Zoomorphology, 127, 143–159. doi: 10.1007/s00435-008-0059-3
Gruhl, A. (2010a). Neuromuscular system of the larva of Fredericella sultana (Bryozoa: Phylactolaemata). Zoologischer Anzeiger, 249(3-4), 139–149. doi: 10.1016/j.jcz.2010.06.001
Gruhl, A. (2010b). Ultrastructure of mesoderm formation and development in Membranipora membranacea (Bryozoa: Gymnolaemata). Zoomorphology, 129(1), 45–60. doi: 10.1007/s00435-009-0099-3
Gruhl, A., & Schwaha, T. F. (2016). Bryozoa (Ectoprocta). In A. Schmidt-Rhaesa, S. Harzsch, & G. Purschke (Eds.), Structure and evolution of invertebrate nervous systems (pp. 324–340). Oxford: Oxford University Press.
Gustus, R. M., & Cloney, R. A. (1972). Ultrastructural similarities between setae of brachiopods and polychaetes. Acta Zoologica, 53(2), 229–233. doi: 10.1111/j.1463-6395.1972.tb00590.x
Gustus, R. M., & Cloney, R. A. (1973). Ultrastructure of the larval compound setae of the polychaete Nereis vexillosa Grube. Journal of Morphology, 140(3), 355–366. doi: 10.1002/jmor.1051400308
Hanken, N.-M., & Harper, D. A. T. (1985). The taxonomy, shell structure, and palaeoecology of the trimerellid brachiopod Gasconsia Northrop. Palaeontology, 28(2), 243–254.
Hanson, J. (1949). Observation on the branchial crown of the Serpulidae (Annelida, Polychaeta). Quarterly Journal of Microscopical Science, 90(3), 221–233.
Haszprunar, G. (1996). The Mollusca: coelomate turbellarians or mesenchymate annelids? In J. D. Taylor (Ed.), Origin and evolutionary radiation of the mollusca (pp. 29–51). London: The Malacological Society of London.
Haszprunar, G. (2000). Is the Aplacophora monophyletic? A cladistic point of view. American Malacological Bulletin, 15, 115–130.
Haszprunar, G., & Wanninger, A. (2008). On the fine structure of the creeping larva of Loxosomella murmanica: additional evidence for a clade of Kamptozoa (Entoprocta) and Mollusca. Acta Zoologica, 89(2). doi: 10.1111/j.1463-6395.2007.00301.x
Hausen, H. (2005). Chaetae and chaetogenesis in polychaetes (Annelida). Hydrobiologia, 535-536(1), 37–52. doi: 10.1007/s10750-004-1836-8
Hay-Schmidt, A. (1992). Ultrastructure and immunocytochemistry of the nervous system of the larvae of Lingula anatina and Glottidia sp. (Brachiopoda). Zoomorphology, 112(4), 189–205. doi: 10.1007/BF01632817
Healy, J. M., Schaefer, K., & Haszprunar, G. (1995). Spermatozoa and spermatogenesis in a monoplacophoran mollusc, Laevipilina antarctica: Ultrastructure and comparison with other Mollusca. Marine Biology, 122(1), 53–65. doi: 10.1007/BF00349277
Hejnol, A. (2010). A twist in time—the evolution of spiral cleavage in the light of animal phylogeny. Integrative and Comparative Biology, 50(5), 695–706. doi: 10.1093/icb/icq103
Hoare, R. D. (2009). Aesthete canals in the Chiton Euleptochiton spatulatus (Polyplacophora, Mollusca) from the Pennsylvanian of Ohio. The Ohio Journal of Science, 109(3), 48–51.
Hoare, R. D., & Mapes, R. H. (1986). The polyplacophoran “Chiton” carbonarius Stevens, 1858, in North America and new related species. Journal of Paleontology, 60(3), 627–635. doi: 10.1017/S0022336000022150
Hodgson, A. N., & Reunov, A. A. (1994). Ultrastructure of the spermatozoon and spermatogenesis of the brachiopods Discinisca tenuis (Inarticulata) and Kraussina rubra (Articulata). Invertebrate Reproduction & Development, 25(1), 23–31. doi: 10.1080/07924259.1994.9672365
Holborow, P. L., Laverack, M. S., & Barber, V. C. (1969). Cilia and other surface structures of the trochophore of Harmothoë imbricata (Polychaeta). Zeitschrift Für Zellforschung Und Mikroskopische Anatomie, 98(2), 246–261. doi: 10.1007/BF00338328
Holmer, L. E., & Caron, J.-B. (2006). A spinose stem group brachiopod with pedicle from the Middle Cambrian Burgess Shale. Acta Zoologica, 87, 273–290. doi: 10.1111/j.1463-6395.2006.00241.x
Holmer, L. E., Pettersson Stolk, P. S., Skovsted, C. B., Balthasar, U., & Popov, L. E. (2009). The enigmatic early Cambrian Salanygolina – A stem group of rhynchonelliform chileate brachiopods? Palaeontology, 52(1), 1–10. doi: 10.1111/j.1475-4983.2008.00831.x
Holmer, L. E., Popov, L. E., & Bassett, M. G. (2014). Ordovician–Silurian Chileida—first post-Cambrian records of an enigmatic group of Brachiopoda. Journal of Paleontology, 88(3), 488–496. doi: 10.1666/13-104
Holmer, L. E., Popov, L. E., Koneva, S. P., & Rong, J.-Y. (1997). Early Cambrian Lingulellotreta (Lingulata, Brachiopoda) from south Kazakhstan (Malyi Karatau Range) and South China (eastern Yunnan). Journal of Paleontology, 71(4), 577–584. doi: 10.1017/s0022336000040063
Holmer, L. E., Skovsted, C. B., & Brock, G. A. (2006). First record of canaliform shell structure from the Lower Cambrian paterinate brachiopod ~Askepasma~ from South Australia. Memoirs of the Association of Australasian Palaeontologists, 32(1998), 1–5. doi: 10.1016/j.jep.2011.11.008.An
Holmer, L. E., Skovsted, C. B., Brock, G. A., Valentine, J. L., & Paterson, J. R. (2008). The Early Cambrian tommotiid Micrina, a sessile bivalved stem group brachiopod. Biology Letters, 4, 724–728. doi: 10.1098/rsbl.2008.0277
Holmer, L. E., Zhang, Z.-F., Topper, T. P., Popov, L. E., & Claybourn, T. M. (2018b). The attachment strategies of Cambrian kutorginate brachiopods: the curious case of two pedicle openings and their phylogenetic significance. Journal of Paleontology, 92(1), 33–39. doi: 10.1017/jpa.2017.76
Humphreys, W. J. (1962). Electron microscope studies on eggs of Mytilus edulis. Journal of Ultrastructure Research, 7(5-6), 467–487. doi: 10.1016/S0022-5320(62)90041-2
Hunt, S. (1972). Scleroprotein and chitin in the exoskeleton of the ectoproct Flustra foliacea. Comparative Biochemistry and Physiology Part B: Comparative Biochemistry, 43(3), 571–574. doi: 10.1016/0305-0491(72)90140-X
Jacquet, S. M., Brock, G. A., & Paterson, J. R. (2014). New data on Oikozetetes (Mollusca, Halkieriidae) from the lower Cambrian of South Australia. Journal of Paleontology, 88(5), 1072–1084. doi: 10.1666/13-137
Jeuniaux, C. (1971). Chitinous structures. Comprehensive Biochemistry, 26(C), 595–632.
Kaas, P. (1981). Scandinavian species of Leptochiton Gray, 1847 (Mollusca, Polyplacophora). Sarsia, 66(3), 217–229. doi: 10.1080/00364827.1981.10414541
Katsuno, S., & Sasaki, T. (2008). Comparative histology of radula-supporting structures in Gastropoda. Malacologia, 50(1), 13–56. doi: 10.4002/0076-2997-50.1.13
Keay, J. (2007). Larval development of the polychaete annelid, Serpula vermicularis. Oregon Institute of Marine Biology.
Kniprath, E. (1980). Larval development of the shell and the shell gland in Mytilus (Bivalvia). Wilhelm Roux’s Archives of Developmental Biology, 188(3), 201–204. doi: 10.1007/BF00849049
Larsson, C. M., Skovsted, C. B., Brock, G. A., Balthasar, U., Topper, T. P., & Holmer, L. E. (2014). Paterimitra pyramidalis from South Australia: scleritome, shell structure and evolution of a lower Cambrian stem group brachiopod. Palaeontology, 57(2), 417–446. doi: 10.1111/pala.12072
Leise, E. M. (1986). Chiton integument: Development of sensory organs in juvenile Mopalia muscosa. Journal of Morphology, 189(1), 71–87.
Leise, E. M. (1988). Sensory organs in the hairy girdles of some mopaliid chitons. American Malacological Bulletin, 6(1), 141–151.
Leise, E. M., & Cloney, R. (1982). Chiton integument: ultrastructure of the sensory hairs of Mopalia muscosa (Mollusca: Polyplacophora). Cell and Tissue Research, 223(1), 43–59. doi: 10.1007/BF00221498
Lemche, H. M., & Wingstrand, K. G. (1959). The anatomy of Neopilina galatheae Lemche, 1957 (Mollusca, Tryblidiacea). Galathea Report, 3, 9–73.
Lewis, C. A., Leighton, D. L., & Vacquier, V. D. (1980). Morphology of abalone spermatozoa before and after the acrosome reaction. Journal of Ultrastructure Research, 72(1), 39–46. doi: 10.1016/S0022-5320(80)90133-1
Li, G.-X., & Holmer, L. E. (2004). Early Cambrian lingulate brachiopods from the Shaanxi Province, China. GFF, 126(2), 193–211. doi: 10.1080/11035890401262193
Lindberg, D. R. (1985). Aplacophorans, Monoplacophorans, Polyplacophorans, Scaphopods: The Lesser Classes. Notes for a Short Course: Studies in Geology, 13, 230–247. doi: 10.1017/S0271164800001202
Lundin, K., & Schander, C. (2001). Ciliary ultrastructure of neomeniomorphs (Mollusca, Neomeniomorpha = Solenogastres). Invertebrate Biology, 120(4), 342–349.
Lundin, K., Schander, C., & Todt, C. (2009). Ultrastructure of epidermal cilia and ciliary rootlets in Scaphopoda. Journal of Molluscan Studies, 75(1), 69–73. doi: 10.1093/mollus/eyn042
Lüter, C. (1995). Ultrastructure of the metanephridia of Terebratulina retusa and Crania anomala (Brachiopoda). Zoomorphology, 115(2), 99–107. doi: 10.1007/BF00403258
Lüter, C. (2000). Ultrastructure of larval and adult setae of Brachiopoda. Zoologischer Anzeiger, 239(1), 75–90.
Lüter, C. (2003). Brachiopod larval setae – a key to the phylum’s ancestral life cycle? In Brachiopods past and present (pp. 46–55). doi: 10.1201/9780203210437-12
Lüter, C. (2016). Brachiopoda. In A. Schmidt-Rhaesa, S. Harzsch, & G. Purschke (Eds.), Structure and evolution of invertebrate nervous systems (pp. 341–350). Oxford: Oxford University Press.
MacKay, S., & Hewitt, R. A. (1978). Ultrastructural studies on the brachiopod pedicle. Lethaia, 11(4), 331–339. doi: 10.1111/j.1502-3931.1978.tb01891.x
Madison, A. (2017). Laminar shell structure of Antigonambonites planus (Pander, 1830) (Brachiopoda, Billingsellida). Estonian Journal of Earth Sciences, 66, 183–187. doi: 10.3176/earth.2017.17
Marek, L. (1963). New knowledge on the morphology of Hyolithes. Sborník Geologických Věd: Paleontologie, 1, 53–73, pls1–4.
Marek, L. (1966). New hyolithid genera from the Ordovician of Bohemia [Nové rody hyolitů z Českého ordoviku]. Časopis Národního Muzea, Oddíl Přírodovědný, 135, 89–92.
Marek, L. (1967). The Class Hyolitha in the Caradoc of Bohemia. Sborník Geologických Věd. Paleontologie, 9, 51–112, pls1–10.
Marek, L. (1976). The distribution of the Mediterranean Ordovician Hyolitha. In M. G. Bassett (Ed.), The ordovician system: Proceedings of a palaeontological association symposium (pp. 491–499). Cardiff: University of Wales Press; National Museum of Wales.
Marlow, H., Tosches, M. A., Tomer, R., Steinmetz, P. R., Lauri, A., Larsson, T., & Arendt, D. (2014). Larval body patterning and apical organs are conserved in animal evolution. BMC Biology, 12(1), 7. doi: 10.1186/1741-7007-12-7
Martel, A. L. (2000). Identification of settling and early postlarval stages of mussels (Mytilus spp.) from the Pacific coast of North America, using prodissoconch morphology and genomic DNA. Marine Biology, 137, 811–818. doi: 10.1007/s002270000
Martin, G. G., Romero, K., & Miller-Walker, C. (1983). Fine structure of the ovary in the red abalone Haliotis rufescens (Mollusca: Gastropoda). Zoomorphology, 103(2), 89–102. doi: 10.1007/BF00312240
Martí Mus, M., & Bergström, J. (2005). The morphology of hyolithids and its functional implications. Palaeontology, 48(6), 1139–1167. doi: 10.1111/j.1475-4983.2005.00511.x
McLean, J. H. (1979). A new monoplacophoran limpet from the continental shelf off southern California. Contributions to Science and Natural History, Los Angeles County Museum, 307, 1–19.
Menzies, R. J., & Layton, W. (1962). A new species of monoplacophoran mollusc, Neopilina (Neopilina) veleronis from the slope of the Cedros Trench, Mexico. Journal of Natural History Series 13, 5(55), 401–406. doi: 10.1080/00222936208651264
Meyer, N. P., Boyle, M. J., Martindale, M. Q., & Seaver, E. C. (2010). A comprehensive fate map by intracellular injection of identified blastomeres in the marine polychaete Capitella teleta. EvoDevo, 1, 8. doi: 10.1186/2041-9139-1-8
Miles, C. M., Hadfield, M. G., & Wayne, M. L. (2007). Heritability for egg size in the serpulid polychaete Hydroides elegans. Marine Ecology Progress Series, 340(May 2014), 155–162. doi: 10.3354/meps340155
Morton, J. E. (1959). The habits and feeding organs of Dentalium entalis. Journal of the Marine Biological Association of the United Kingdom, 38(2), 225–238. doi: 10.1017/S0025315400006032
Moysiuk, J., Smith, M. R., & Caron, J.-B. (2017). Hyoliths are Palaeozoic lophophorates. Nature, 541(7637), 394–397. doi: 10.1038/nature20804
Nielsen, C. (1966). On the life-cycle of some Loxosomatidae (Entoprocta). Ophelia, 3(1), 221–247. doi: 10.1080/00785326.1966.10409644
Nielsen, C. (1971). Entoproct life-cycles and the entoproct/ectoproct relationship. Ophelia, 9(2), 209–341. doi: 10.1080/00785326.1971.10430095
Nielsen, C. (1987). Structure and function of metazoan ciliary bands and their phylogenetic significance. Acta Zoologica, 68(4), 205–262. doi: 10.1111/j.1463-6395.1987.tb00892.x
Nielsen, C. (1991). The development of the brachiopod Crania (Neocrania) anomala (O. F. Müller) and its phylogenetic significance. Acta Zoologica, 72(1), 7–28. doi: 10.1111/j.1463-6395.1991.tb00312.x
Nielsen, C., & Rostgaard, J. (1976). Structure and function of an entoproct tentacle with a discussion of ciliary feeding types. Ophelia, 15(2), 115–140. doi: 10.1080/00785326.1976.10425453
Niijima, L. (1965). The acrosome reaction in Mytilus edulis: I. Fine structure of the intact acrosome. The Journal of Cell Biology, 25(2), 243–248. doi: 10.1083/jcb.25.2.243
Nikitin, I. F., & Popov, L. E. (1984). Brachiopods and biostratigraphy of the Middle and Upper Ordovician of the Chingiz Range. In Brachiopods and biostratigraphy of the middle and upper ordovician of the chingiz range, part ii: Brachiopods from the bestamak and sargaldak formations (middle ordovician) (pp. 126–166). Alma-Ata: Nauka.
Nützel, A., Lehnert, O., & Frýda, J. (2006). Origin of planktotrophy—evidence from early molluscs. Evolution & Development, 8, 325–330. doi: 10.1111/j.1525-142X.2006.00105.x
Okusu, A. (2002). Embryogenesis and Development of Epimenia babai (Mollusca Neomeniomorpha). Biological Bulletin (Woods Hole), 203(1), 87–103.
Orrhage, L. (1971). Light and electron microscope studies of some annelid setae. Acta Zoologica, 52(1), 157–169. doi: 10.1111/j.1463-6395.1971.tb00555.x
Orrhage, L., & Müller, M. C. M. (2005). Morphology of the nervous system of Polychaeta (Annelida). Hydrobiologia, 535-536(1), 79–111. doi: 10.1007/s10750-004-4375-4
Pardos, F., Roldán, C., Benito, J., & Emig, C. C. (1991). Fine structure of the tentacles of Phoronis australis Haswell (Phoronida, Lophophorata). Acta Zoologica, 72(2), 81–90. doi: 10.1111/j.1463-6395.1991.tb00320.x
Parkinson, D., Curry, G. B., Cusack, M., & Fallick, A. E. (2005). Shell structure, patterns and trends of oxygen and carbon stable isotopes in modern brachiopod shells. Chemical Geology, 219(1-4), 193–235. doi: 10.1016/j.chemgeo.2005.02.002
Parry, L. A., Edgecombe, G. D., Eibye-Jacobsen, D., & Vinther, J. (2016). The impact of fossil data on annelid phylogeny inferred from discrete morphological characters. Proceedings of the Royal Society B: Biological Sciences, 283(1837), 20161378. doi: 10.1098/rspb.2016.1378
Parry, L., & Caron, J.-B. (2019). Canadia spinosa and the early evolution of the annelid nervous system. Science Advances, 5(9), eaax5858. doi: 10.1126/sciadv.aax5858
Paterson, J. R., Brock, G. A., & Skovsted, C. B. (2009). Oikozetetes from the early Cambrian of South Australia: implications for halkieriid affinities and functional morphology. Lethaia, 42(2), 199–203. doi: 10.1111/j.1502-3931.2008.00132.x
Pennerstorfer, M., & Scholtz, G. (2012). Early cleavage in Phoronis muelleri (Phoronida) displays spiral features. Evolution and Development, 14(6), 484–500. doi: 10.1111/ede.12002
Pilger, J. F. (1982). Ultrastructure of the tentacles of Themiste lageniformis (Sipuncula). Zoomorphology, 100(2), 143–156. doi: 10.1007/BF00310360
Pojeta, J., Runnegar, B. N., Morris, N. J., & Newell, N. D. (1972). Rostroconchia: A new class of bivalved mollusks. Science, 177(4045), 264–267. doi: 10.1126/science.177.4045.264
Ponder, W. F., & Lindberg, D. R. (1997). Towards a phylogeny of gastropod molluscs: an analysis using morphological characters. Zoological Journal of the Linnean Society, 119(2), 83–265. doi: 10.1111/j.1096-3642.1997.tb00137.x
Popov, L. E., Holmer, L. E., & Gorjansky, V. J. (1997). Late Ordovician and Early Silurian trimerellide brachio-pods from Kazakhstan. Journal of Paleontology, 71(4), 584–598. doi: 10.1017/S0022336000040075
Porter, S. M. (2008). Skeletal microstructure indicates chancelloriids and halkieriids are closely related. Palaeontology, 51(4), 865–879. doi: 10.1111/j.1475-4983.2008.00792.x
Reed, C. G. (1988). The reproductive biology of the gymnolaemate bryozoan Bowerbankia gracilis (Ctenostomata: Vesiculariidae). Ophelia, 29(1), 1–23. doi: 10.1080/00785326.1988.10430816
Reed, C. G., & Cloney, R. A. (1982). The larval morphology of the marine bryozoan Bowerbankia gracilis (Ctenostomata: Vesicularioidea). Zoomorphology, 100(1), 23–54. doi: 10.1007/BF00312198
Reger, J. F. (1967). A fine structure study on the organization and innervation of pharyngeal glands and associated ciliated epithelium in the annelid Enchytraeus albidus. Journal of Ultrastructure Research, 20, 451–461. doi: 10.1016/S0022-5320(67)80112-6
Reunov, A. A., & Klepal, W. (2004). Ultrastructural study of spermatogenesis in Phoronopsis harmeri (Lophophorata, Phoronida). Helgoland Marine Research, 58(1), 229. doi: 10.1007/s10152-003-0153-3
Reynolds, P. D., & Okusu, A. (1999). Phylogenetic relationships among families of the Scaphopoda (Mollusca). Zoological Journal of the Linnean Society, 126(2), 131–154. doi: 10.1111/j.1096-3642.1999.tb00151.x
Rice, M. E. (1988). Observations on development and metamorphosis of Siphonosoma cumanense with comparative remarks on Sipunculus nudus (Sipuncula, Sipunculidae). Bulletin of Marine Science, 42(1), 1–15.
Rice, M. E. (1993). Sipuncula. In F. W. Harrison & M. E. Rice (Eds.), Microscopic antomy of invertebrates, volume 12: Onychophora, chilopoda, and lesser protostomata (Vol. 12, pp. 237–326). New York: Wiley-Liss.
Richter, S., Loesel, R., Purschke, G., Schmidt-Rhaesa, A., Scholtz, G., Stach, T., … Harzsch, S. (2010). Invertebrate neurophylogeny: suggested terms and definitions for a neuroanatomical glossary. Frontiers in Zoology, 7, 29. doi: 10.1186/1742-9994-7-29
Robson, S. P., & Pratt, B. R. (2001). Cambrian and Ordovician linguliform brachiopods from the Shallow Bay Formation (Cow Head Group), western Newfoundland. Journal of Paleontology, 75(2), 241–260. doi: 10.1017/s0022336000018060
Rogalla, N. S., & Amler, M. R. W. (2003). Biogeographical distribution patterns in Mid- and Late Palaeozoic Conocardioida (Mollusca: Rostroconchia). 242, 51–69.
Rogalla, N. S., Carter, J. G., & Pojeta, J. (2003). SHELL MICROSTRUCTURE OF THE LATE CARBONIFEROUS ROSTROCONCH MOLLUSC APOTOCARDIUM LANTERNA (BRANSON, 1965). JOURNAL OF PALEONTOLOGY, 77(4), 20.
Rouse, G. W. (1999). Trochophore concepts: ciliary bands and the evolution of larvae in spiralian Metazoa. Biological Journal of the Linnean Society, 66(4), 411–464. doi: 10.1111/j.1095-8312.1999.tb01920.x
Rouse, G. W. (2000). Bias? What bias? The evolution of downstream larval-feeding in animals. Zoologica Scripta, 29(3), 213–236. doi: 10.1046/j.1463-6409.2000.00040.x
Runnegar, B. N. (1978). Origin and evolution of the Class Rostroconchia. Philosophical Transactions of the Royal Society B: Biological Sciences, 284, 319–333.
Runnegar, B., & Bentley, C. (1983). Anatomy, ecology and affinities of the Australian Early Cambrian bivalve Pojetaia runnegari Jell. Journal of Paleontology, 57(1), 73–92.
Ruppert, E. E., & Carle, K. J. (1983). Morphology of metazoan circulatory systems. Zoomorphology, 103(3), 193–208. doi: 10.1007/BF00310477
Ruppert, E. E., & Rice, M. E. (1995). Functional organization of dermal coelomic canals in Sipunculus nudus (Sipuncula) with a discussion of respiratory designs in sipunculans. Invertebrate Biology, 114(1), 51–63. doi: 10.2307/3226953
Santagata, S. (2002). Structure and metamorphic remodeling of the larval nervous system and musculature of Phoronis pallida (Phoronida). Evolution and Development, 4(1), 28–42. doi: 10.1046/j.1525-142x.2002.01055.x
Santagata, S. (2004). Larval evelopment of Phoronis pallida (Phoronida): implications for morphological convergence and divergence among larval body plans. Journal of Morphology, 259(3), 347–358. doi: 10.1002/jmor.10205
Scheltema, A. H. (1993). Aplacophora as progenetic aculiferans and the coelomate origin of mollusks as the sister taxon of Sipuncula. Biological Bulletin, 184(1), 57–78. doi: 10.2307/1542380
Scheltema, A. H. (2014). The original molluscan radula and progenesis in Aplacophora revisited. Journal of Natural History, 48(45-48), 2855–2869. doi: 10.1080/00222933.2014.959573
Schopf, T. J. M., & Manheim, F. T. (1967). Chemical composition of Ectoprocta (Bryozoa). Journal of Paleontology, 41(5), 1197–1225. doi: 10.2307/1302092
Schulze, A., Cutler, E. B., & Giribet, G. (2005). Reconstructing the phylogeny of the Sipuncula. Hydrobiologia, 535-536(1), 277–296. doi: 10.1007/s10750-004-4404-3
Schwabe, E. (2010). Illustrated summary of chiton terminology. Spixiana, 3(2), 171–194.
Schwaha, T. F., & Wanninger, A. (2015). The serotonin-lir nervous system of the Bryozoa (Lophotrochozoa): a general pattern in the Gymnolaemata and implications for lophophore evolution of the phylum Evolutionary developmental biology and morphology. BMC Evolutionary Biology, 15(1), 223. doi: 10.1186/s12862-015-0508-9
Schweigkofler, M., Bartolomaeus, T., & Salvini-Plawen, L. von. (1998). Ultrastructure and formation of hooded hooks in Capitella capitata (Annelida, Capitellida). Zoomorphology, 118(2), 117–128. doi: 10.1007/s004350050062
Shimek, R. L. (1988). The functional morphology of scaphopod captacula. The Veliger, 30(3), 213–221.
Shunkina, K. V., Zaytseva, O. V., Starunov, V. V., & Ostrovsky, A. N. (2015). Comparative morphology of the nervous system in three phylactolaemate bryozoans. Frontiers in Zoology, 12, 28. doi: 10.1186/s12983-015-0112-2
Skovsted, C. B., Betts, M. J., Topper, T. P., & Brock, G. A. (2015). The early Cambrian tommotiid genus Dailyatia from South Australia. Memoirs of the Association of Australasian Palaeontologists, 48(1), 1–117.
Skovsted, C. B., Brock, G. A., Paterson, J. R., Holmer, L. E., & Budd, G. E. (2008). The scleritome of Eccentrotheca from the Lower Cambrian of South Australia: Lophophorate affinities and implications for tommotiid phylogeny. Geology, 36, 171–174. doi: 10.1130/g24385a.1
Skovsted, C. B., Pan, B., Topper, T. P., Betts, M. J., Li, G., & Brock, G. A. (2016). The operculum and mode of life of the lower Cambrian hyolith Cupitheca from South Australia and North China. Palaeogeography, Palaeoclimatology, Palaeoecology, 443, 123–130. doi: 10.1016/j.palaeo.2015.11.042
Smith, M. R. (2012a). Morphology, ecology, and affinity of soft-bodied ‘molluscs’ from Cambrian Burgess Shale-type deposits (PhD thesis; p. 257). University of Toronto; University of Toronto, Toronto, Ontario.
Smith, M. R. (2012b). Mouthparts of the Burgess Shale fossils Odontogriphus and Wiwaxia: implications for the ancestral molluscan radula. Proceedings of the Royal Society B: Biological Sciences, 279(1745), 4287–4295. doi: 10.1098/rspb.2012.1577
Smith, M. R. (2014). Ontogeny, morphology and taxonomy of the soft-bodied Cambrian ’mollusc’ Wiwaxia. Palaeontology, 57(1), 215–229. doi: 10.1111/pala.12063
Steiner, G. (1992). Phylogeny and classification of Scaphopoda. Journal of Molluscan Studies, 58(4), 385–400. doi: 10.1093/mollus/58.4.385
Steiner, G. (1998). Phylogeny of Scaphopoda (Mollusca) in the light of new anatomical data on the Gadilinidae and some Problematica, and a reply to Reynolds. Zoologica Scripta, 27(1), 73–82. doi: 10.1111/j.1463-6409.1998.tb00429.x
Storch, V., & Herrmann, K. (1978). Podocytes in the blood vessel linings of Phoronis muelleri (Phoronida, Tentaculata). Cell and Tissue Research, 190(3), 553–556. doi: 10.1007/bf00219564
Streng, M., Butler, A. D., Peel, J. S., Garwood, R. J., & Caron, J.-B. (2016). A new family of Cambrian rhynchonelliformean brachiopods (Order Naukatida) with an aberrant coral-like morphology. Palaeontology, 59(2), 269–293. doi: 10.1111/pala.12226
Sumner-Rooney, L. H., Schrödl, M., Lodde-Bensch, E., Lindberg, D. R., Heß, M., Brennan, G. P., & Sigwart, J. D. (2015). A neurophylogenetic approach provides new insight to the evolution of Scaphopoda. Evolution and Development, 17(6), 337–346. doi: 10.1111/ede.12164
Sun, H.-J., Malinky, J. M., Zhu, M.-Y., & Huang, D.-Y. (2018). Palaeobiology of orthothecide hyoliths from the Cambrian Manto Formation of Hebei Province, North China. Acta Palaeontologica Polonica, 63(1), 87–101. doi: 10.4202/app.00413.2017
Sun, Y., & Qiu, J.-W. (2012). Serpulidae (Annelida: Polychaeta) from Hong Kong. Zootaxa, 3423, 1–42.
Sutton, M. D., & Sigwart, J. D. (2012). A chiton without a foot. Palaeontology, 55(2), 401–411. doi: 10.1111/j.1475-4983.2011.01126.x
Sutton, M. D., Briggs, D. E. G., Siveter, D. J., Siveter, D. J., & Sigwart, J. D. (2012). A Silurian armoured aplacophoran and implications for molluscan phylogeny. Nature, 490(7418), 94–97. doi: 10.1038/nature11328
Temereva, E. N. (2016). Phoronida. In A. Schmidt-Rhaesa, S. Harzsch, & G. Purschke (Eds.), Structure and evolution of invertebrate nervous systems (pp. 351–359). Oxford: Oxford University Press.
Temereva, E. N. (2017). Innervation of the lophophore suggests that the phoronid Phoronis ovalis is a link between phoronids and bryozoans. Scientific Reports, 7, 14440. doi: 10.1038/s41598-017-14590-8
Temereva, E. N., & Kosevich, I. A. (2016). The nervous system of the lophophore in the ctenostome Amathia gracilis provides insight into the morphology of ancestral ectoprocts and the monophyly of the lophophorates. BMC Evolutionary Biology, 16(1), 181. doi: 10.1186/s12862-016-0744-7
Temereva, E. N., & Kuzmina, T. V. (2017). The first data on the innervation of the lophophore in the rhynchonelliform brachiopod Hemithiris psittacea: what is the ground pattern of the lophophore in lophophorates? BMC Evolutionary Biology, 17(1), 172. doi: 10.1186/s12862-017-1029-5
Thomas, R. D., & Vinther, J. (2012). Implications of the occurrence of paired anterior chaetae in the late early Cambrian mollusc Pelagiella from the Kinzers Formation of Pennsylvania for relationships among taxa and early evolution of the Mollusca. Geological Society of America (GSA) Annual Meeting 2012 Abstracts, 326.
Topper, T. P., Harper, D. A. T., & Ahlberg, P. (2013). Reappraisal of the brachiopod Acrotreta socialis von Seebach, 1865: clarifying 150 years of confusion. GFF, 135(2), 191–203. doi: 10.1080/11035897.2013.811440
Topper, T. P., Holmer, L. E., Skovsted, C. B., Brock, G. A., Balthasar, U., Larsson, C. M., … Harper, D. A. T. (2013). The oldest brachiopods from the lower Cambrian of South Australia. Acta Palaeontologica Polonica, 58(1), 93–109. doi: 10.4202/app.2011.0146
Torrey, H. B. (1901). On Phoronis pacifica sp. nov. Biological Bulletin, 2(6), 282–288. doi: 10.2307/1535705
Treves, K., Traub, W., Weiner, S., & Addadi, L. (2003). Aragonite formation in the chiton (Mollusca) girdle. Helvetica Chimica Acta, 86(4), 1101–1112. doi: 10.1002/hlca.200390096
Valent, M., Fatka, O., Szabad, M., Micka, V., & Marek, L. (2012). Two new orthothecids from the Cambrian of the Barrandian area (Hyolitha, Skryje-Týřovice Basin, Czech Republic). Bulletin of Geosciences, 87(2), 241–248. doi: 10.3140/bull.geosci.1142
Vendrasco, M. J., & Runnegar, B. N. (2004). Late Cambrian and Early Ordovician stem group chitons (Mollusca: Polyplacophora) from Utah and Missouri. Journal of Paleontology, 78(4), 675–689.
Vendrasco, M. J., Checa, A. G., & Porter, S. M. (2017). Periostracum and fibrous shell microstructure in the unusual Cambrian hyolith Cupitheca. Spanish Journal of Palaeontology, 32(1), 95–108.
Vendrasco, M. J., Fernandez, C. Z., Eernisse, D. J., & Runnegar, B. N. (2008). Aesthete canal morphology in the Mopaliidae (Polyplacophora). American Malacological Bulletin, 25(1), 51–69.
Vinther, J., & Nielsen, C. (2005). The Early Cambrian Halkieria is a mollusc. Zoologica Scripta, 34(1), 81–89. doi: 10.1111/j.1463-6409.2005.00177.x
Vinther, J., Jell, P. A., Kampouris, G., Carney, R., Racicot, R. A., & Briggs, D. E. G. (2012). The origin of multiplacophorans – convergent evolution in aculiferan molluscs. Palaeontology, 55(5), 1007–1019. doi: 10.1111/j.1475-4983.2012.01180.x
Vinther, J., Parry, L., Briggs, D. E. G., & Van Roy, P. (2017). Ancestral morphology of crown-group molluscs revealed by a new Ordovician stem aculiferan. Nature, 542, 471–474. doi: 10.1038/nature21055
Vinther, J., Van Roy, P., & Briggs, D. E. G. (2008). Machaeridians are Palaeozoic armoured annelids. Nature, 451(7175), 185–188. doi: 10.1038/nature06474
von Salvini-Plawen, L., & Steiner, G. (1996). Synapomorphies and plesiomorphies in higher classification of Mollusca. In J. D. Taylor (Ed.), Origin and evolutionary radiation of the mollusca (pp. 29–51). London: The Malacological Society of London.
Voronezhskaya, E. E., Nezlin, L. P., Odintsova, N. A., Plummer, J. T., & Croll, R. P. (2008). Neuronal development in larval mussel Mytilus trossulus (Mollusca: Bivalvia). Zoomorphology, 127(2), 97–110. doi: 10.1007/s00435-007-0055-z
Waller, T. R. (1998). Origin of the molluscan class Bivalvia and a phylogeny of major groups. In P. A. Johnston & J. W. Haggart (Eds.), Bivalves: An Eon of Evolution (pp. 1–45). Calgary: University of Calgary Press.
Wanninger, A. (2009). Shaping the things to come: ontogeny of lophotrochozoan neuromuscular systems and the tetraneuralia concept. Biological Bulletin, 216(3), 293–306. doi: 10.1086/bblv216n3p293
Wanninger, A., & Haszprunar, G. (2001). The expression of an engrailed protein during embryonic shell formation of the tusk-shell, Antalis entalis (Mollusca, Scaphopoda). Evolution & Development, 3(5), 312. doi: 10.1046/j.1525-142X.2001.01034.x
Wanninger, A., & Haszprunar, G. (2002a). Chiton myogenesis: perspectives for the development and evolution of larval and adult muscle systems in molluscs. Journal of Morphology, 251(2), 103–113. doi: 10.1002/jmor.1077
Wanninger, A., & Haszprunar, G. (2002b). Muscle development in Antalis entalis (Mollusca, Scaphopoda) and its significance for scaphopod relationships. Journal of Morphology, 254(1), 53–64. doi: 10.1002/jmor.10004
Wanninger, A., Fuchs, J., & Haszprunar, G. (2007). Anatomy of the serotonergic nervous system of an entoproct creeping-type larva and its phylogenetic implications. Invertebrate Biology, 126(3), 268–278. doi: 10.1111/j.1744-7410.2007.00097.x
Wanninger, A., Koop, D., Bromham, L., Noonan, E., & Degnan, B. M. (2005). Nervous and muscle system development in Phascolion strombus (Sipuncula). Development Genes and Evolution, 215(10), 509–518. doi: 10.1007/s00427-005-0012-0
Watkins, R. (2002). New record of the trimerellid brachiopod Gasconsia, a rare Silurian Lazarus taxon. Journal of Paleontology, 76(1), 185–186. doi: 10.1666/0022-3360(2002)076<0185:nrottb>2.0.co;2
Williams, A., Carlson, S. J., Brunton, C. H. C., Holmer, L. E., Popov, L. E., Mergl, M., … Wright, A. D. (2000). Linguliformea, Craniiformea, and Rhynchonelliformea (part). In Treatise on Invertebrate Paleontology, Part H, Brachiopoda (Revised) (Vol. 2 & 3, pp. 1–919). doi: 10.17161/dt.v0i0.5215
Williams, A., Cusack, M., & Buckman, J. O. (1998a). Chemico-structural phylogeny of the discinoid brachiopod shell. Philosophical Transactions of the Royal Society B: Biological Sciences, 353(1378), 2005–2038. doi: 10.1098/rstb.1998.0350
Williams, A., James, M. A., Emig, C. C., Mackay, S., Rhodes, M. C., Cohen, B. L., … Richardson, J. R. (1997). Introduction. In Treatise on Invertebrate Paleontology, Part H, Brachiopoda (Revised) (Vol. 1, pp. 1–539). doi: 10.17161/dt.v0i0.5560
Williams, A., Popov, L. E., Holmer, L. E., & Cusack, M. (1998b). The diversity and phylogeny of the paterinate brachiopods. Palaeontology, 41, 221–262.
Wingstrand, K. G. (1985). On the anatomy and relationships of Recent Monoplacophora. Galathea Report, 16, 7–94.
Young, C. M. (2002). Atlas of Marine Invertebrate Larvae (p. 626). New York: Academic Press.
Zardus, J. D., & Morse, M. P. (1998). Embryogenesis, morphology and ultrastructure of the pericalymma larva of Acila castrensis (Bivalvia: Protobranchia: Nuculoida). Invertebrate Biology, 117(3), 221. doi: 10.2307/3226988
Zhang, Z.-F., Han, J., Zhang, X.-L., Liu, J.-N., Guo, J.-F., & Shu, D.-G. (2007a). Note on the gut preserved in the Lower Cambrian Lingulellotreta (Lingulata, Brachiopoda) from southern China. Acta Zoologica, 88(1), 65–70. doi: 10.1111/j.1463-6395.2007.00252.x
Zhang, Z.-F., Holmer, L. E., Popov, L. E., & Shu, D.-G. (2011). An obolellate brachiopod with soft-part preservation from the Early Cambrian Chengjiang fauna of China. Journal of Paleontology, 85(3), 460–463. doi: 10.1666/10-121.1
Zhang, Z.-F., Holmer, L. E., Skovsted, C. B., Brock, G. A., Budd, G. E., Fu, D., … Li, G.-X. (2013). A sclerite-bearing stem group entoproct from the early Cambrian and its implications. Scientific Reports, 3, 1066. doi: 10.1038/srep01066
Zhang, Z.-F., Li, G.-X., Holmer, L. E., Brock, G. A., Balthasar, U., Skovsted, C. B., … Shu, D.-G. (2014). An early Cambrian agglutinated tubular lophophorate with brachiopod characters. Scientific Reports, 4, 4682. doi: 10.1038/srep04682
Zhang, Z.-F., Shu, D.-G., Emig, C. C., Zhang, X.-L., Han, J., Liu, J.-N., … Guo, J.-F. (2007b). Rhynchonelliformean brachiopods with soft-tissue preservation from the early Cambrian Chengjiang Lagerstätte of South China. Palaeontology, 50, 1391–1402. doi: 10.1111/j.1475-4983.2007.00725.x
Zhang, Z.-F., Shu, D.-G., Han, J., & Liu, J.-N. (2005). Morpho-anatomical differences of the Early Cambrian Chengjiang and Recent lingulids and their implications. Acta Zoologica, 86, 277–288. doi: 10.1111/j.1463-6395.2005.00211.x
Zhang, Z.-F., Smith, M. R., & Shu, D.-G. (2015). New reconstruction of the Wiwaxia scleritome, with data from Chengjiang juveniles. Scientific Reports, 5, 14810. doi: 10.1038/srep14810
Zhang, Z.-L., Skovsted, C. B., & Zhang, Z.-F. (2018). A hyolithid without helens preserving the oldest hyolith muscle scars; palaeobiology of Paramicrocornus from the Shujingtuo Formation (Cambrian Series 2) of South China. Palaeogeography, Palaeoclimatology, Palaeoecology, 489, 1–14. doi: 10.1016/j.palaeo.2017.07.021
Zhang, Z.-L., Zhang, Z.-F., & Wang, H.-Z. (2016). Epithelial cell moulds preserved in the earliest acrotretid brachiopods from the Cambrian (Series 2) of the Three Gorges area, China. GFF, 138(4), 455–466. doi: 10.1080/11035897.2016.1143528
Zhao, F.-C., Smith, M. R., Yin, Z.-J., Zeng, H., Li, G.-X., & Zhu, M.-Y. (2017). Orthrozanclus elongata n. sp. and the significance of sclerite-covered taxa for early trochozoan evolution. Scientific Reports, 7(1), 16232. doi: 10.1038/s41598-017-16304-6
Zhuravlev, A. Y., Wood, R. A., & Penny, A. M. (2015). Ediacaran skeletal metazoan interpreted as a lophophorate. Proceedings of the Royal Society B: Biological Sciences, 282(1818), 20151860. doi: 10.1098/rspb.2015.1860
Zimmer, R. L., & Woollacott, R. M. (2013). Metamorphosis, ancestrulae and coloniality in Bryozoan life cycles. In R. M. Woollacott & R. L. Zimmer (Eds.), Biology of bryozoans (pp. 91–142). Elsevier.